# EDGAR Filing Document

**Accession Number:** 0001851961
**File Stem:** 0000929638-26-002280
**Filing Date:** 2026-6
**Character Count:** 106819
**Document Hash:** c368eb16cafc76536b0dcc93eaa1b9cf
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0000929638-26-002280.hdr.sgml**: 20260618

**ACCESSION NUMBER**: 0000929638-26-002280

**CONFORMED SUBMISSION TYPE**: 424B5

**PUBLIC DOCUMENT COUNT**: 1

**FILED AS OF DATE**: 20260618

**DATE AS OF CHANGE**: 20260618

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** GCT Semiconductor Holding, Inc.
- **CENTRAL INDEX KEY:** 0001851961
- **STANDARD INDUSTRIAL CLASSIFICATION:** SEMICONDUCTORS & RELATED DEVICES [3674]
- **ORGANIZATION NAME:** 04 Manufacturing
- **EIN:** 862171699
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 424B5
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 333-286316
- **FILM NUMBER:** 261103211

**BUSINESS ADDRESS:**
- **STREET 1:** 2290 NORTH 1ST STREET
- **STREET 2:** SUITE 201
- **CITY:** SAN JOSE
- **STATE:** CA
- **ZIP:** 95131
- **BUSINESS PHONE:** 408-434-6040

**MAIL ADDRESS:**
- **STREET 1:** 2290 NORTH 1ST STREET
- **STREET 2:** SUITE 201
- **CITY:** SAN JOSE
- **STATE:** CA
- **ZIP:** 95131

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** Concord Acquisition Corp III
- **DATE OF NAME CHANGE:** 20210318

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| | |
|:---|:---|
| **PROSPECTUS SUPPLEMENT**<br> (To the Prospectus dated April 9, 2025) | **Filed Pursuant to Rule 424**(**b)(5)**<br> **Registration No**. **333-286316**<br>|

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&nbsp;&nbsp;&nbsp;&nbsp;<br>

### GCT Semiconductor Holding, Inc.

### <sub>Up to $120,000,000 of Common Stock</sub>
We have previously entered into an At Market Issuance Sales Agreement (the "sales agreement") dated April 1, 2025, with B. Riley Securities, Inc. and H.C. Wainwright & Co., LLC (the "sales agents"), as our sales agents, relating to shares of our common stock, par value $0.0001 per share ("Common Stock"). We are filing this prospectus supplement to reflect an increase in our existing at the market offering program to allow for the issuance of an additional $45.0 million in shares of our Common Stock pursuant to the Sales Agreement, for a total of $120.0 million (inclusive of any amounts sold prior to the date hereof). This prospectus supplement hereby amends and replaces the prior ATM prospectus dated April 9, 2025.

Sales of our Common Stock, if any, under this prospectus will be made by any method that is deemed to be an "at the market offering" as defined in Rule 415(a)(4) under the Securities Act of 1933, as amended (the "Securities Act"). Our Common Stock is listed on The New York Stock Exchange ("NYSE") under the symbol "GCTS." The last reported sale price of our Common Stock on The NYSE on June 15, 2026 was $2.61 per share.

The compensation of our sales agents for sales of Common Stock pursuant to the sales agreement shall be a commission rate up to 3.0% of the gross proceeds from each sale. The net proceeds from any sale under this prospectus will be used as described under "*Use of Proceeds*" in this prospectus. There is no arrangement for funds to be received in escrow, trust or similar arrangement.

In connection with the sale of the Common Stock on our behalf, each sales agent will be deemed to be an "underwriter" within the meaning of the Securities Act, and the compensation of the sales agents will be deemed to be underwriting commissions or discounts. We have also agreed to provide indemnification and contribution to the sales agents with respect to certain civil liabilities, including liabilities under the Securities Act. See "*Plan of Distribution*."

The sales agents are not required to sell any specific number or dollar amount of Common Stock but will use their commercially reasonable efforts, as our agents and subject to the terms of the sales agreement, to sell the Common Stock offered, as instructed by us. The offering of Common Stock pursuant to this prospectus will terminate upon the earlier of (i) the sale of all Common Stock subject to this prospectus or (ii) the termination of the sales agreement by us or by the sales agents pursuant to the terms of the sales agreement.

***We are an "emerging growth company" under federal securities laws and are subject to reduced public company reporting requirements. Investing in our Common Stock involves a high degree of risk. See "Risk Factors" beginning on page 4 of this prospectus and the "Risk Factors" section contained in our reports filed with the Securities and Exchange Commission which are incorporated by reference herein for a discussion of information that should be considered in connection with an investment in our Common Stock.***

**Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.**

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| | |
|:---|:---|
| **B. Riley Securities** | **H.C. Wainwright & Co.** |

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#### <br>

#### The date of this prospectus supplement is June 18, 2026.

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#### **TABLE OF CONTENTS**

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| | |
|:---|:---|
|  | **Page** |
| [ABOUT THIS PROSPECTUS SUPPLEMENT](#about_this_prospectus1) | [S-1](#about_this_prospectus1) |
| [PROSPECTUS SUPPLEMENT SUMMARY](#prospectus_summary1) | [S-2](#prospectus_summary1) |
| [THE OFFERING](#the_offering1) | [S-3](#the_offering1) |
| [RISK FACTORS](#risk_factors1) | [S-4](#RISKFACTORS1) |
| [FORWARD-LOOKING STATEMENTS](#FORWARD-LOOKINGSTATEMENTS) | [S-6](#FORWARD-LOOKINGSTATEMENTS) |
| [USE OF PROCEEDS](#use_of_proceeds1) | [S-8](#use_of_proceeds1) |
| [DESCRIPTION OF COMMON STOCK](#description_of_common_stock1) | [S-9](#description_of_common_stock1) |
| [PLAN OF DISTRIBUTION](#plan_of_distribution1) | [S-10](#plan_of_distribution1) |
| [LEGAL MATTERS](#legal_matters1) | [S-12](#legal_matters1) |
| [EXPERTS](#experts1) | [S-12](#experts1) |

---

---

| | |
|:---|:---|
| [WHERE YOU CAN FIND MORE INFORMATION](#where_you_can_find_more_information1) | [S-12](#where_you_can_find_more_information1) |
| [DOCUMENTS INCORPORATED BY REFERENCE](#documents_incorporated_by_reference1) | [S-12](#documents_incorporated_by_reference1) |

---

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| | |
|:---|:---|
| **** <br>**Prospectus** | **** <br>**Page** |
| [ABOUT THIS PROSPECTUS](#ABOUTTHISPROSPECTUS) | [1](#ABOUTTHISPROSPECTUS) |
| [PROSPECTUS SUMMARY](#PROSPECTUSSUMMARY) | [2](#PROSPECTUSSUMMARY) |
| [RISK FACTORS](#RISKFACTORS2) | [3](#RISKFACTORS2) |
| [WHERE YOU CAN FIND MORE INFORMATION](#WHEREYOUCANFINDMOREINFORM) | [4](#WHEREYOUCANFINDMOREINFORM) |
| [DOCUMENTS INCORPORATED BY REFERENCE](#documents_incorporated_by_reference1) | [4](#documents_incorporated_by_reference1) |
| [CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS](#CAUTIONARYNOTEREGARDINGFO) | [5](#CAUTIONARYNOTEREGARDINGFO) |
| [USE OF PROCEEDS](#USEOFPROCEEDS2) | [6](#USEOFPROCEEDS2) |
| [DESCRIPTION OF COMMON STOCK](#description_of_common_stock1) | [7](#description_of_common_stock1) |
| [DESCRIPTION OF PREFERRED STOCK](#DESCRIPTIONOFPREFERREDSTO) | [8](#DESCRIPTIONOFPREFERREDSTO) |
| [DESCRIPTION OF WARRANTS](#DESCRIPTIONOFWARRANTS) | [9](#DESCRIPTIONOFWARRANTS) |
| [DESCRIPTION OF DEBT SECURITIES](#DESCRIPTIONOFDEBTSECURITI) | [11](#DESCRIPTIONOFDEBTSECURITI) |
| [DESCRIPTION OF RIGHTS](#DESCRIPTIONOFRIGHTS) | [15](#DESCRIPTIONOFRIGHTS) |
| [DESCRIPTION OF UNITS](#DESCRIPTIONOFUNITS) | [15](#DESCRIPTIONOFUNITS) |
| [PLAN OF DISTRIBUTION](#PLANOFDISTRIBUTION) | [16](#PLANOFDISTRIBUTION) |
| [LEGAL MATTERS](#LEGALMATTERS) | [17](#LEGALMATTERS) |
| [EXPERTS](#EXPERTS) | [17](#EXPERTS) |

---

**The distribution of this prospectus supplement and sale of these securities in certain jurisdictions may be restricted. Persons in possession of this prospectus supplement are required to inform themselves about and observe any such restrictions. We are not making an offer of these securities in any jurisdiction where the offer is not permitted.**

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#### ABOUT THIS PROSPECTUS SUPPLEMENT
This document is in two parts. The first part is this prospectus supplement, which contains specific information about the terms on which we are offering and selling our Common Stock and also adds to and updates information contained in the accompanying prospectus and documents incorporated by reference herein and therein. Under this prospectus supplement and the accompanying prospectus, we may offer and sell shares of our common stock having an aggregate offering price of up to $120,000,000 from time to time through or to the sales agents at prices and on terms to be determined by market conditions at the time of the offering. The second part is the accompanying prospectus, which contains and incorporates by reference more general information, some of which may not apply to this offering. This prospectus supplement and the accompanying prospectus are part of a registration statement on Form S-3 that we filed with the U.S. Securities and Exchange Commission (the "SEC") using a "shelf" registration process. We urge you to carefully read this prospectus supplement, the information incorporated by reference, the accompanying prospectus, and any free writing prospectus that we authorize to be distributed to you before buying any of the securities being offered under this prospectus supplement. This prospectus supplement may supplement, update or change information contained in the accompanying prospectus. To the extent that any statement that we make in this prospectus supplement is inconsistent with statements made in the accompanying prospectus or any documents incorporated by reference therein, the statements made in this prospectus supplement will be deemed to modify or supersede those made in the accompanying prospectus and such documents incorporated by reference therein.

We have not, and the sales agents have not, authorized anyone to provide you with information other than the information that we have provided or incorporated by reference in this prospectus supplement, the accompanying base prospectus or any other prospectus supplement and your reliance on any unauthorized information or representation is at your own risk. This prospectus supplement may be used only in jurisdictions where offers and sales of these securities are permitted. You should assume that the information appearing in this prospectus supplement is accurate only as of the date of this prospectus supplement and that any information we have incorporated by reference is accurate only as of the date of the document incorporated by reference, regardless of the time of delivery of this prospectus supplement, or any sale of our Common Stock. Our business, financial condition and results of operations may have changed since those dates.

We further note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference herein were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreements, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. This prospectus supplement and the accompanying prospectus is an offer to sell only the securities offered hereby and only under circumstances and in jurisdictions where it is lawful to do so. No dealer, salesperson or other person is authorized to give any information or to represent anything not contained in this prospectus, accompanying prospectus, and any free writing prospectuses prepared by or on behalf of us or to which we have referred you or are incorporated by reference. This prospectus supplement is not an offer to sell securities, and it is not soliciting an offer to buy securities, in any jurisdiction where the offer or sale is not permitted.

Unless otherwise stated, all references in this prospectus supplement to "we," "us," "our," "GCT," the "Company" and similar designations refer to GCT Semiconductor Holding Inc.

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#### PROSPECTUS SUPPLEMENT SUMMARY
*This summary highlights certain information contained in or incorporated by reference in this prospectus supplement and the accompanying prospectus about us and this offering. Because it is a summary, it does not contain all of the information that you should consider before investing. Before investing in our securities, you should read this entire prospectus supplement and the accompanying prospectus carefully, including the section under the heading "Risk Factors" in this prospectus supplement beginning on page S-5 and in the documents incorporated by reference in this prospectus supplement and the accompanying prospectus, and the documents we have incorporated by reference in this prospectus supplement and the accompanying prospectus, along with the financial statements and accompanying notes incorporated by reference in this prospectus supplement and the accompanying prospectus.*

#### Business Summary
*Company Overview*

GCT Semiconductor Holding, Inc. ("GCT") was founded in Silicon Valley, California in 1998 and is a fabless semiconductor company that specializes in the design, manufacturing and sale of communication semiconductors, including high-speed wireless communication technologies such as 5G/4.75G/4.5G/4G transceivers ("RF") and modems, which are essential for a wide variety of industrial, B2B and consumer applications. We have successfully developed and supplied communication semiconductor chipsets and modules to leading wireless operators worldwide, as well as to original design manufacturers ("ODMs") and original equipment manufacturers ("OEMs") for portable wireless routers (e.g., Mobile Router/MiFi), indoor and outdoor fixed wireless routers (e.g., CPE), industrial machine-to-machine ("M2M") applications and smartphones.

We oversee sales, marketing, and accounting operations from our headquarters in San Jose, California. We conduct product design, development, and customer support through our fully owned subsidiaries, GCT Research, Inc. ("GCT R") and MTH, Inc., both of which are located in South Korea. GCT R serves as our research and development center. In addition, we utilize separate sales offices for local technical support and sales in Taiwan, China, and Japan.

Our current product portfolio includes RF and modem chipsets based on 4th generation ("4G"), known as Long Term Evolution ("LTE"), technology offering a variety of chipsets differentiated by speed and functionality. These include 4G LTE, 4.5G LTE Advanced (twice the speed of LTE), and 4.75G LTE Advanced-Pro (four times the speed of LTE) chipsets. We also develop and sell cellular IoT chipsets for low-speed mobile networks such as eMTC/NB- IOT/Sigfox, and other network protocols.

*Corporate Information*

Our principal executive offices are located at 2290 North 1st Street, Suite 201 San Jose, CA 95131, and our telephone number is (408) 434-6040.

#### Implications of Being a Smaller Reporting Company
We are a "smaller reporting company" meaning that the market value of our Common Stock held by non-affiliates is less than $250.0 million measured on the last business day of our second fiscal quarter or our annual revenue is less than $100.0 million during the most recent completed fiscal year and the market value of our Common Stock held by non-affiliates is less than $700.0 million measured on the last business day of our second fiscal quarter. Accordingly, we may provide less public disclosure than larger public companies, including the inclusion of only two years of audited financial statements and only two years of management's discussion and analysis of financial condition and results of operations disclosure. As a result, the information that we provide to our stockholders may be different than you might receive from other public reporting companies in which you hold equity interests.

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#### THE OFFERING

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| | |
|:---|:---|
| **Common Stock offered by us** | Common Stock having an aggregate offering price of up to $120,000,000. The actual number of shares outstanding after this offering will vary depending on the number of shares sold and issued and the sales price of such shares. |
| **Plan of distribution** | "At the market offering" that may be made from time to time to or through B. Riley Securities, Inc. and H.C. Wainwright & Co., LLC as sales agents or principal. See "*Plan of Distribution*" in this prospectus. |
| **Common Stock to be outstanding after this offering, assuming an offering price of $2.61 per share(1)** | Up to 115,834,651 shares, assuming the total amount available under the sales agreement is $64.9 million and an assumed offering price of $2.61 per share for future sales, which was the closing price of our Common Stock on the NYSE on June 15, 2026. The actual number of shares issued will vary depending on the sales price under this offering. |
| **Use of proceeds** | We intend to use the net proceeds from this offering for general corporate purposes, which may include working capital needs, capital expenditures, repayment or refinancing of indebtedness, acquisitions of complementary businesses or assets, stock repurchases and redemptions of securities. See "*Use of Proceeds*." |
| **Risk factors** | Investing in our Common Stock involves a high degree of risk. You should carefully consider all of the information in this prospectus and the documents incorporated by reference in this prospectus. In particular, see "*Risk Factors*" beginning on page 4 of this prospectus. |
| **NYSE symbol** | "GCTS" |

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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(1) The common stock outstanding after the offering is based on 90,963,011 shares of our Common Stock outstanding as of June 15, 2026 and excludes the following:

• 2,118,608 shares of our Common Stock reserved for future issuance under our 2024 Incentive Compensation Plan;

• 600,000 shares of our Common Stock reserved for future issuance under our 2024 Employee Stock Purchase Plan;

• 332,738 shares of our Common Stock issuable upon exercise of outstanding options at a weighted-average exercise price of $0.11 per share;

• 191,530 shares of our Common Stock subject to restricted stock units awarded under our 2011 Incentive Compensation Plan;

• 1,130,665 shares of our Common Stock subject to restricted stock units awarded under our 2024 Incentive Compensation Plan; and

• 41,917,875 shares of our Common Stock issuable upon exercise of outstanding warrants at a weighted-average exercise price of $7.37 per share.

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#### RISK FACTORS
*Investing in our securities involves a high degree of risk. Before making an investment decision, you should carefully consider the risks described below and under the section titled "Risk Factors" in our most recent Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K incorporated by reference in this prospectus supplement and the accompanying prospectus, any amendment or update thereto reflected in our subsequent filings with the SEC, and all of the other information in this prospectus supplement and the accompanying prospectus and the documents that we have incorporated by reference herein and therein, including our financial statements and related notes incorporated by reference in this prospectus supplement and the accompanying prospectus. If any of these risks is realized, our business, financial condition, results of operations and prospects could be materially and adversely affected. In that event, the trading price of our Common Stock could decline and you could lose part or all of your investment. Additional risks and uncertainties that are not yet identified or that we think are immaterial may also materially harm our business, operating results and financial condition and could result in a complete loss of your investment.*

#### Risks Related to our Common Stock and the Offering

#### Our management will have broad discretion as to the use of proceeds from this offering and we may not use the proceeds effectively.
Our management will have broad discretion in the application of the net proceeds from this offering, if any, and could spend the proceeds in ways that do not improve our results of operations or enhance the value of our Common Stock. You will be relying on the judgment of our management concerning these uses and you will not have the opportunity, as part of your investment decision, to assess whether the proceeds are being used appropriately. The failure of our management to apply these funds effectively could result in unfavorable returns and uncertainty about our prospects, each of which could cause the price of our Common Stock to decline.

***There may be future dilution of our Common Stock as a result of future sales of our Common Stock, which could adversely impact our stock price.***

The issuance of shares of our Common Stock from time to time pursuant to the sales agreement may have a dilutive effect on our earnings per share, which could adversely impact the market price of our Common Stock. The actual amount of dilution and the effect on the market price of our Common Stock, if any, will be based on numerous factors, particularly the actual number of shares issued pursuant to the sales agreement, the use of proceeds and the return generated by the investments acquired with the net proceeds, and cannot be determined at this time. In addition, the issuance and sale of substantial amounts of our Common Stock, or the perception that such issuances and sales may occur, could adversely affect the market price of our Common Stock and impair our ability to raise capital through the sale of additional equity securities. Additionally, the sale of shares of Common Stock in this offering will increase the supply of available shares, which may result in a decrease in the price of our Common Stock.

***The shares of our Common Stock offered under this prospectus will be sold in "at the market offerings", and investors who buy shares at different times will likely pay different prices.***

Investors who purchase shares under this prospectus at different times will likely pay different prices, and so may experience different outcomes in their investment results. We will have discretion, subject to market demand, to vary the timing, prices, and numbers of shares sold, and to determine the minimum sales price for shares sold. Investors may experience declines in the value of their shares as a result of share sales made in connection with "at the market offerings" at prices lower than the prices they paid.

#### The actual number of shares we will issue under the sales agreement, at any one time or in total, is uncertain.
Subject to certain limitations in the sales agreement and compliance with applicable law, we and our sales agents may mutually agree to sell shares of our Common Stock under a placement notice at any time throughout the term of the sales agreement. The number of shares that are sold by our sales agents in connection with any placement notice will fluctuate based on the market price of the shares of our Common Stock during the sales period and limits we set with our sales agents. Because the price per share of each share sold will fluctuate based on the market price

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of our shares of Common Stock during the sales period, it is not possible to predict the number of shares that will ultimately be issued.

#### Our stock price may fluctuate significantly, and investors may not be able to sell their shares at an attractive price.
The trading price of our Common Stock may be volatile and subject to wide price fluctuations in response to various factors including:

<br> • changes in financial estimates, including our ability to meet our future revenue and operating profit or loss projections;

<br> • changes in earnings estimates or recommendations by securities analysts;

<br> • fluctuations in our operating results or those of our customers, operators or other semiconductor companies;

<br> • commercial deployment and upgrade of 4G and 5G wireless networks;

<br> • economic developments in the semiconductor or mobile and wireless industries as a whole;

<br> • general economic conditions and slow or negative growth of related markets;

<br> • announcements by us or our customers or competitors of acquisitions, new products, significant contracts or orders, commercial relationships or capital commitments;

<br> • announcements regarding intellectual property litigation involving us or our competitors;

<br> • changes in the financial estimates of our competitors;

<br> • our ability to develop and market new and enhanced products on a timely basis;

<br> • changes in the pricing and costs of manufacturing;

<br> • commencement of or our involvement in litigation;

<br> • any major change in our board of directors or management;

<br> • political or social conditions in the markets where we sell our products; and

<br> • changes in governmental regulations.

These and other factors may cause the market price and demand for our Common Stock to fluctuate substantially, which may limit or prevent investors from readily selling their shares of our Common Stock and may otherwise negatively affect the liquidity of our Common Stock. In addition, in the past, when the market price of a stock has been volatile, holders of that stock have sometimes instituted securities class action litigation against the company that issued the stock. If any of our stockholders were to bring a lawsuit against us, we could incur substantial costs defending the lawsuit. Such a lawsuit could also divert the time and attention of our management from our business.

#### An investor's percentage of ownership in the Company may be diluted in the future.
As with any publicly traded company, an investor's percentage ownership in the Company may be diluted in the future because of the issuance of additional Common Stock. From time to time, we have issued and we expect we will continue to issue stock options or restricted stock grants or similar awards to employees, officers, and directors pursuant to our equity incentive award plans. Investors in our equity securities may experience dilution as these awards vest and are exercised by their holders and as the restrictions lapse on the restricted stock grants. We also may issue Common Stock, preferred stock or warrants of the Company to purchase Common Stock or preferred stock to raise capital to fund our growth initiatives in connection with acquisitions or the settlement of obligations or indebtedness, which would result in further dilution of existing stockholders. The issuance of any such shares of Common Stock, preferred stock or warrants to purchase Common Stock or preferred stock may result in a reduction of the book value or market price of the outstanding shares of our Common Stock.

#### We do not expect to pay dividends to holders of our Common Stock.
We currently intend to retain our future earnings, if any, for the foreseeable future, to repay indebtedness and to fund the development and growth of our business. We do not intend to pay any dividends to holders of our Common Stock. As a result, capital appreciation in the price of our Common Stock, if any, will be investors' only source of gain or income on an investment in our Common Stock.

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#### FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus and the documents we have filed with the SEC that are incorporated by reference in this prospectus supplement and the accompanying prospectus contain forward-looking statements that involve risks and uncertainties. These statements relate to future periods, future events or our future operating or financial plans or performance. When used in this prospectus supplement, the accompanying prospectus and the documents incorporated herein and therein by reference, the words "anticipate," "believe," "continue," "could," "estimate," "expect," "goal," "intend," "project," "future," "forecast," "may," "might," "outlook," "plan," "possible," "potential," "predict," "project," "target," "strategy," "seem," "should," "seeks," "scheduled," "will," "would," and similar expressions are intended to identify forward-looking statements.

The forward-looking statements are based on the current expectations of our management and are inherently subject to uncertainties and changes in circumstances and their potential effects and speak only as of the date of such statement. These forward-looking statements involve a number of risks, uncertainties or other assumptions that may cause actual results or performance to be materially different from those expressed or implied by these forward-looking statements. These risks and uncertainties include, but are not limited to, the following:

<br> • our ability to successfully commercialize, scale, and achieve market adoption of our 5th generation ("5G") products, including through collaboration agreements with our major partners;

<br> • our financial and business performance, including our financial projections and business metrics;

<br> • macroeconomic conditions, including labor disputes, fluctuations in the value of the U.S. dollar, capital markets volatility, inflationary pressures, and disruptions to global supply chains;

<br> • the imposition of duties and tariffs and other trade barriers and retaliatory countermeasures implemented by the U.S. and other governments;

<br> • changes in our strategy, future operations, financial position, estimated revenues and losses, forecasts, projected costs, prospects and plans;

<br> • increase in supply chain costs, including raw materials, sourcing, transportation and energy;

<br> • our inability to anticipate the future market demands and future needs of our customers;

<br> • the impact of component shortages, suppliers' lack of production capacity, natural disasters or pandemics on our sourcing operations and supply chain;

<br> • our ability to meet the prospective delivery time for our products and fulfill customer orders;

<br> • our future capital requirements and sources and uses of cash;

<br> • our ability to fund future capital expenditures and to meet our debt service and repayment obligations, including those related to our near-term indebtedness;

<br> • our ability to obtain funding and raise capital for our operations;

<br> • our ability to access the capital markets and credit markets;

<br> • our anticipated financial performance, including gross margin, and the expectation that our future results of operations will fluctuate on a quarterly basis for the foreseeable future;

<br> • our expected capital expenditures, cost of revenue and other future expenses, and the sources of funds to satisfy the liquidity needs of the Company;

<br> • our ability to maintain the listing of shares of our Common Stock on the NYSE;

<br> • technology, cybersecurity, and data privacy risks;

<br> • intense market competition;

<br> • geopolitical conditions, including political instability, civil unrest, sanctions, numerous ongoing wars and armed conflicts, and broader regional or global tensions that may impact economic and market conditions;

<br> • legislative and regulatory risks, including those relating to changes in laws and regulations and the impact of U.S. government shutdowns or other governmental disruptions;

<br> • uncertainties and risks relating to new trade regulations, including tariffs and export control regulations;

<br> • reputational risks; and

<br> • other risks and uncertainties described in the registration statement of which this prospectus supplement forms a part, including those under the section entitled "*Risk Factors*" and those incorporated by reference herein.

Given these risks and uncertainties, you should not place undue reliance on these forward-looking statements. Additional cautionary statements or discussions of risks and uncertainties that could affect our results or the

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achievement of the expectations described in forward-looking statements may also be contained in the documents we incorporate by reference into this prospectus supplement and the accompanying prospectus.

These forward-looking statements made by us in this prospectus supplement, the accompanying prospectus, or any of the documents incorporated by reference in this prospectus supplement and accompanying prospectus speak only as of the date of this prospectus supplement and the accompanying prospectus. We expressly disclaim any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements contained herein to reflect any change in our expectations with regard thereto or any change in events, conditions or circumstances on which any such statement is based, except as required by law or regulation. You should, however, review additional disclosures we make in our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, and Current Reports on Form 8-K filed with the SEC and incorporated herein by reference.

You should read this prospectus supplement, the accompanying prospectus, and the documents that we incorporated by reference in this prospectus supplement and the accompanying prospectus completely and with the understanding that our actual future results, levels of activity and performance as well as other events and circumstances may be materially different from what we expect. We qualify all of our forward-looking statements by these cautionary statements.

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#### USE OF PROCEEDS
We may issue and sell shares of our Common Stock having aggregate gross sale proceeds of up to $120,000,000 from time to time. As of June 15, 2026, we have sold shares of our Common Stock having aggregate gross sale proceeds of $55.1 million.

There can be no assurance that we will be able to sell any shares under or fully utilize the sales agreement with the sales agents as a source of financing. Because there is no minimum offering amount required as a condition to close this offering, the actual total public offering amount, commissions and proceeds to us, if any, are not determinable at this time.

We currently intend to use the net proceeds, if any, from this offering, after deducting the sales agents' commissions and our offering expenses, for general corporate purposes, which may include working capital needs, capital expenditures, repayment or refinancing of indebtedness, acquisitions of complementary businesses or assets, stock repurchases and redemptions of securities. The amounts and timing of our use of proceeds will vary depending on many factors, including regulatory developments, the amount of cash generated or used by our operations, and the rate of growth, if any, of our business and other capital requirements. As a result, we will retain broad discretion in the allocation of the net proceeds, if any, we receive in connection with securities offered pursuant to this prospectus, and investors will be relying on the judgment of our management regarding the application of the proceeds.

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#### DESCRIPTION OF COMMON STOCK
*The following summary of the material terms of our securities is not intended to be a complete summary of the rights and preferences of such securities. The descriptions below are qualified by reference to the actual text of our Second Amended and Restated Certificate of Incorporation (our "Charter"). We urge you to read our Charter in its entirety for a complete description of the rights and preferences of our securities.*

#### Authorized and Outstanding Capital Stock
Our Charter authorizes the issuance of 400,000,000 shares of Common Stock, $0.0001 par value per share and 40,000,000 shares of Preferred Stock, $0.0001 par value.

As of June 15, 2026, there were 90,963,011 shares of Common Stock issued and outstanding and no shares of Preferred Stock issued and outstanding.

#### Voting Power
Except as otherwise provided by the Delaware General Corporation Law ("DGCL") or our Charter and subject to the rights of holders of any series of Preferred Stock, all of the voting power of our stockholders will be vested in the holders of our Common Stock, and each holder of our Common Stock will have one vote for each share held by such holder on all matters voted upon by the stockholders of the Company; provided, however, that, except as otherwise required by law, holders of our Common Stock, as such, will not be entitled to vote on any amendment to our Charter (or on any amendment to a certificate of designations of any series of Preferred Stock) that alters or changes the powers, preferences, rights or other terms of one or more outstanding series of Preferred Stock if the holders of such affected series of Preferred Stock are entitled to vote, either separately or together with the holders of one or more other such series, on such amendment pursuant to our Charter (or pursuant to a certificate of designations of any series of Preferred Stock) or pursuant to the DGCL. There will be no cumulative voting.

#### Dividends
Except as otherwise provided by the DGCL or our Charter, dividends may be declared and paid on our Common Stock from funds lawfully available therefor if, as and when determined by our Board and subject to any preferential dividend rights of any then outstanding shares of Preferred Stock.

#### Liquidation
Upon the dissolution or liquidation or winding up of the affairs of the Company, whether voluntary or involuntary, holders of our Common Stock will be entitled to receive all our assets available for distribution to our stockholders equally on a per share basis, subject to any preferential rights of any then outstanding shares of Preferred Stock and after payment or provision for payment of our debts.

#### Preemptive Rights; Redemption Rights
The holders of our Common Stock will have no preemptive rights to subscribe for any shares of any class of our stock. Our Common Stock will not be convertible into, or exchangeable for, shares of any other class or classes or of any other series of the same class of our capital stock.

#### Listing
Our Common Stock and our Warrants are currently listed on the NYSE under the symbols "GCTS" and "GCTS-WT," respectively.

#### Transfer Agent and Registrar
The transfer agent and registrar for our Common Stock is Continental Stock Transfer & Trust Company.

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#### PLAN OF DISTRIBUTION
One April 1, 2025, we entered into an At Market Issuance Sales Agreement (the "sales agreement") with B. Riley Securities, Inc. and H.C. Wainwright & Co., LLC (the "sales agents"), as our sales agents, under which we may issue and sell shares of our Common Stock from time to time through or to the sales agents. The sales agreement, which originally provided for an aggregate offering amount of up to $75 million, has been increased to an aggregate offering amount of up to $120 million. As of June 15, 2026, we have sold shares of our Common Stock having aggregate gross sale proceeds of $55.1 million. As a result, the Company may sell up to $64.9 million of shares pursuant to this prospectus supplement. The sales agents may sell the Common Stock by any method that is deemed to be an "at the market offering" as defined in Rule 415 promulgated under the Securities Act.

Each time we wish to issue and sell Common Stock under the sales agreement, we will notify the sales agents of the number or dollar value of shares to be issued, the dates on which such sales are anticipated to be made, any limitation on the number of shares that may be sold in one day, any minimum price below which sales may not be made, and other sales parameters as we deem appropriate. Once we have so instructed a sales agent, unless such sales agent declines to accept the terms of such notice, such sales agent has agreed to use its commercially reasonable efforts consistent with its normal trading and sales practices to sell such shares up to the amount specified on such terms. The obligations of the sales agents under the sales agreement to sell our Common Stock are subject to a number of customary conditions that we must meet. We may instruct the sales agents not to sell our Common Stock if the sales cannot be effected at or above the price designated by us in any such instruction. We and the sales agents may suspend the offering of Common Stock upon proper notice to the other party and subject to other conditions. We and the sales agents each have the right, by giving written notice as specified in the sales agreement, to terminate the sales agreement in each party's sole discretion at any time upon five days' prior notice.

Under the terms of the sales agreement, we may also sell our Common Stock to the sales agents, as principal for their own account, at a price negotiated at the time of sale, provided that no sales may be made in a principal transaction without our prior consent.

Unless otherwise specified in the applicable placement notice, settlement for shares of our Common Stock will occur on the trading day following the date on which the sales are made. Sales of our Common Stock as contemplated in this prospectus will be settled through the facilities of The Depository Trust Company or by such other means as we and the sales agents may agree upon. There is no arrangement for funds to be received in an escrow, trust or similar arrangement.

We will pay the sales agents a commission for their services in acting as agents in the sale of Common Stock at a commission rate of up to 3.0% of the gross proceeds from each sale. We previously agreed to reimburse the sales agents for certain specified fees and documented expenses, including the fees and documented expenses of their legal counsel in an amount not to exceed $75,000, which has been paid in connection with the execution of the sales agreement, plus an additional amount not to exceed $5,000 per fiscal quarter on an ongoing basis during the term of the sales agreement, as provided in the sales agreement. We have also agreed to reimburse the sales agents for certain specified fees and documented expenses, including the fees and documented expenses of their legal counsel in connection with the filing of this prospectus supplement in an amount not to exceed $30,000. Because there is no minimum offering amount required as a condition to close this offering, the actual total public offering amount, commissions and proceeds to us, if any, are not determinable at this time. In addition, we will pay H.C. Wainwright & Co., LLC an additional financial advisory fee of up to 0.27% of the gross proceeds received by us from the sale of Common Stock made through or to the sales agents pursuant to the sales agreement. We estimate that the total expenses for the offering, excluding compensation payable to the sales agents and expense reimbursement under the terms of the sales agreement, will be up to approximately $316,120.

In addition, the sales agreement provides that we will not (i) take any action designed to cause or result in, or that constitutes or would reasonably be expected to constitute, the stabilization or manipulation of the price of any of our securities to facilitate the sale or resale of Common Stock, or (ii) sell, bid for, or purchase Common Stock in violation of Regulation M, or pay anyone any compensation for soliciting purchases of the Common Stock under the sales agreement other than the sales agents.

In connection with the sale of the Common Stock on our behalf, each sales agent will be deemed to be an "underwriter" within the meaning of the Securities Act as amended, and its compensation will be deemed to be underwriting commissions or discounts. We have agreed to provide indemnification and contribution to the sales agents with respect to certain liabilities, including civil liabilities under the Securities Act.

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The offering of our Common Stock pursuant to the sales agreement will terminate upon the earlier of (1) the issuance and sale of all Common Stock subject to the sales agreement; and (2) the termination of the sales agreement as described therein.

In April 2024, the Company entered into a common stock purchase agreement (the "Purchase Agreement") and a related registration rights agreement (the "Registration Rights Agreement") with B. Riley Principal Capital II, LLC, an affiliate of B. Riley Securities, Inc. ("B. Riley Principal Capital II"). Upon the terms and subject to the satisfaction of the conditions set forth in the Purchase Agreement, the Company has the right, in its sole discretion, to sell to B. Riley Principal Capital II, from time to time, up to $50.0 million in aggregate gross purchase price of shares of the Company's Common Stock, subject to certain limitations contained in the Purchase Agreement, during the term of 24 months. Pursuant to the Registration Rights Agreement, the Company has filed a registration statement on Form S-1 to register the resale of shares of Common Stock that are sold to B. Riley Principal Capital II under the Purchase Agreement. Sales of Common Stock by the Company to B. Riley Principal Capital II pursuant to the Purchase Agreement, and the timing of any such sales, are solely at the option of the Company, and the Company is under no obligation to sell any securities to B. Riley Principal Capital II under the Purchase Agreement. As of May 1, 2026, the Company has sold an aggregate of 2,438,737 shares of Common Stock and the Purchase Agreement has been terminated as of May 1, 2026 pursuant to the Purchase Agreement.

The sales agents and their respective affiliates have in the past and may in the future provide various investment banking and/or other financial services for us and/or our affiliates, for which services they may in the future receive customary fees. To the extent required by Regulation M under the Exchange Act, the sales agents will not engage in any market making activities involving our Common Stock while the offering is ongoing under this prospectus.

This summary of the material provisions of the sales agreement does not purport to be a complete statement of its terms and conditions. A copy of the sales agreement is filed with the SEC as an exhibit to the registration statement of which this prospectus is a part. See "*Where You Can Find More Information*."

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#### LEGAL MATTERS
The validity of the shares of Common Stock offered by this prospectus were passed upon by Morgan, Lewis & Bockius LLP, Palo Alto, California. Certain matters will be passed upon for the sales agents by Duane Morris LLP, New York, New York.

#### EXPERTS
The consolidated financial statements of the Company as of December 31, 2025 and 2024, and for each of the two years in the period ended December 31, 2025, incorporated in this registration statement by reference to the Annual Report on Form 10-K for the year ended December 31, 2025, have been so incorporated in reliance on the report (which contains an explanatory paragraph relating to the Company's ability to continue as a going concern as described in Note 1 to the consolidated financial statements) of BPM LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

**WHERE YOU CAN FIND MORE INFORMATION**

We have filed a registration statement on Form S-3 with the SEC under the Securities Act. This prospectus supplement and the accompanying prospectus are part of the registration statement but the registration statement includes and incorporates by reference additional information and exhibits. We file annual, quarterly and current reports, proxy statements and other information with the SEC. The SEC maintains a web site that contains reports, proxy and information statements and other information regarding companies, such as ours, that file documents electronically with the SEC. The address of that site on the worldwide web is www.sec.gov.

#### DOCUMENTS INCORPORATED BY REFERENCE
The SEC allows us to "incorporate by reference" the information we file with the SEC under the Exchange Act, which means that we can disclose important information to you by referring you to those documents. Information incorporated by reference is considered to be a part of this prospectus, and information that we file later with the SEC will automatically update, modify and, where applicable, supersede this information. We incorporate by reference into this prospectus supplement the specific documents listed below and all documents filed by us with the SEC pursuant to Section 13(a), 13(c), 14, or 15(d) of the Exchange Act between the date of this prospectus supplement and the termination of the Offering of Securities under this prospectus supplement (other than, in each case, documents or information deemed to be furnished and not filed in accordance with SEC rules), which future filings shall be deemed to be incorporated by reference into this prospectus supplement and to be part of this prospectus supplement from the date we subsequently file such documents. The SEC file number for these documents is 1-41013.

<br> • [Our Annual Report on Form 10-K for the fiscal year ended December 31, 2025, filed with the SEC on March 25, 2026](https://www.sec.gov/Archives/edgar/data/1851961/000095017025044438/gcts-20241231.htm);

<br> • [Our Quarterly Report on Form 10-Q for the quarter ended March 31, 2026, filed with the SEC on May 12, 2026](https://www.sec.gov/Archives/edgar/data/1851961/000095017025044438/gcts-20241231.htm);

<br> • Our Current Reports on Form 8-K filed with the SEC on January 29, 2026 and February 25, 2026; and

<br> • The description of our securities contained in Exhibit 4.9 to the Annual Report on Form 10-K for the year ended December 31, 2025, filed with the SEC on March 25, 2026.

Any statement contained in this prospectus supplement or in any document incorporated by reference into this prospectus supplement shall be deemed to be modified or, where applicable, superseded for the purposes of this prospectus supplement to the extent that a statement contained in this prospectus supplement or any subsequently filed document that also is incorporated by reference into this prospectus supplement modifies or supersedes such prior statement. Any statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this prospectus supplement.

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We will provide to each person, including any beneficial owner, to whom a prospectus supplement is delivered, upon written or oral request and without charge, a copy of the documents referred to above that we have incorporated by reference into this prospectus supplement and a copy of the registration statement of which this prospectus supplement is a part. You can request copies of such documents if you write us at our principal executive offices at 2290 North 1st Street, Suite 201 San Jose, CA 95131, or call our telephone number at (408) 434-6040.

Exhibits to the documents will not be sent, however, unless those exhibits have specifically been incorporated by reference into such document. You may also obtain copies of our SEC filings statement as described above under the heading "*Where You Can Find More Information*."

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#### <br>

#### PROSPECTUS
**$200,000,000**

**GCT Semiconductor Holding, Inc.**

**Common Stock** 

**Preferred Stock** 

**Debt Securities** 

**Warrants**

**Rights**

**Units**

We, from time to time, may offer and sell, in one or more offerings, up to $200,000,000 of any combination of shares of our common stock (Common Stock), shares of our preferred stock, debt securities, warrants (Warrants), rights and units. We may offer and sell these securities in amounts, at prices and on terms determined at the time of the offering.

This prospectus describes the general terms of these securities and the general manner in which these securities will be offered. Each time securities are offered under this prospectus, we will provide a prospectus supplement and attach it to this prospectus. The prospectus supplement will contain more specific information about the terms of the offering and the offered securities and may also supplement, update or amend information contained in this prospectus.

We may offer and sell these securities to or through underwriters, dealers or agents, directly to purchasers or through a combination of these methods. If we use underwriters, dealers or agents to sell these securities, we will name them and describe their compensation arrangements in the prospectus supplement relating to such offering.

Our Common Stock and Warrants are traded on the New York Stock Exchange under the symbols GCTS and GCTS-WT, respectively. On March 28, 2025, the closing price of our Common Stock was $1.78 per share, and the closing price of our Warrants was $0.0861 per Warrant.

***We are an emerging growth company under federal securities laws and are subject to reduced public company reporting requirements. Investing in our securities involves a high degree of risk. See the section titled Risk Factors beginning on page 3 of this prospectus to read about factors you should consider before buying our securities.***

**Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus or any accompanying prospectus supplement is truthful or complete. Any representation to the contrary is a criminal offense.**

**The date of this prospectus is April 9, 2025**

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**TABLE OF CONTENTS**

**<u>Page</u>**

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| | |
|:---|:---|
| ABOUT THIS PROSPECTUS | 1 |
| PROSPECTUS SUMMARY | 2 |
| RISK FACTORS | 3 |
| WHERE YOU CAN FIND MORE INFORMATION | 4 |
| DOCUMENTS INCORPORATED BY REFERENCE | 4 |
| CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS | 5 |
| USE OF PROCEEDS | 6 |
| DESCRIPTION OF COMMON STOCK | 7 |
| DESCRIPTION OF PREFERRED STOCK | 8 |
| DESCRIPTION OF WARRANTS | 9 |
| DESCRIPTION OF DEBT SECURITIES | 11 |
| DESCRIPTION OF RIGHTS | 15 |
| DESCRIPTION OF UNITS | 15 |
| PLAN OF DISTRIBUTION | 16 |
| LEGAL MATTERS | 17 |
| EXPERTS | 17 |

---

**The distribution of this prospectus and sale of these securities in certain jurisdictions may be restricted. Persons in possession of this prospectus are required to inform themselves about and observe any such restrictions. We are not making an offer of these securities in any jurisdiction where the offer is not permitted.**

**All references in this prospectus to we, us, our, and GCT refer only to GCT Semiconductor Holding, Inc. and not to any existing or future subsidiaries of GCT Semiconductor Holding, Inc., unless the context otherwise requires.**

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**ABOUT THIS PROSPECTUS**

This document is called a prospectus and is part of a registration statement on Form S-3 that we filed with the SEC using a shelf registration process. Under this shelf process, we may offer and sell, from time to time in one or more offerings, the securities described in this prospectus. This prospectus provides you with a general description of the securities we may offer and the general manner in which these securities may be offered. Each time we sell securities under this prospectus, we will provide you with a prospectus supplement that will contain specific information about the terms of that offering and the offered securities. That prospectus supplement may also supplement, update or amend information contained in or incorporated by reference into this prospectus.

The registration statement of which this prospectus is a part contains additional information about us and the securities we may offer by this prospectus. Specifically, we have filed and incorporated by reference certain legal documents that control the terms of the securities offered by this prospectus as exhibits to the registration statement. We will file or incorporate by reference certain other legal documents that will control the terms of the securities we may offer by this prospectus as exhibits to the registration statement or to reports we file with the SEC that are incorporated by reference into this prospectus.

In addition, we may prepare and deliver one or more free writing prospectuses to you in connection with any offering of securities under this prospectus. Any such free writing prospectus may contain additional information about us, our business, the offered securities, the manner in which such securities are being offered, our intended use of the proceeds from the sale of such securities, risks relating to our business or an investment in such securities or other information.

This prospectus and certain of the documents incorporated by reference into this prospectus contain, and any accompanying prospectus supplement or free writing prospectus that we deliver to you may contain, summaries of information contained in documents that we have filed or will file as exhibits to our SEC filings. Such summaries do not purport to be complete and are subject to, and qualified in their entirety by reference to, the actual documents filed with the SEC.

Copies of the registration statement of which this prospectus is a part and of the documents incorporated by reference into this prospectus may be obtained as described below under the heading *Documents Incorporated by Reference* and under the heading *Where You Can Find More Information*.

You should not assume that the information contained in this prospectus, the registration statement to which this prospectus is a part, any accompanying prospectus supplement or any free writing prospectus that we deliver to you is accurate as of any date other than the date of such documents or that the information incorporated by reference into this prospectus is accurate as of any date other than the date of the document incorporated by reference. Our business, operating results, financial condition, capital resources and prospects may have changed since that date.

**You should rely only on the information contained in or incorporated by reference into this prospectus, the registration statement of which this prospectus is a part, any accompanying prospectus supplement, and any free writing prospectus that we deliver to you. We have not authorized anyone to provide you with different information. If you receive any other information, you should not rely on it.**

**** 

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**PROSPECTUS SUMMARY**

*This summary highlights selected information appearing elsewhere in this prospectus or the documents incorporated by reference herein. Because it is a summary, it may not contain all of the information that may be important to you. To understand this offering fully, you should read this entire prospectus, the registration statement of which this prospectus is a part and the documents incorporated by reference herein carefully, including the information set forth under the heading* Risk Factors *and our financial statements.*

 

**Business Summary**

 

*Company Overview*

GCT Semiconductor Holding, Inc. (GCT) was founded in Silicon Valley, California in 1998 and is a fabless semiconductor company that specializes in the design, manufacturing and sale of communication semiconductors, including high-speed wireless communication technologies such as 5G/4.75G/4.5G/4G transceivers (RF) and modems, which are essential for a wide variety of industrial, B2B and consumer applications. We have successfully developed and supplied communication semiconductor chipsets and modules to leading wireless operators worldwide, as well as to original design manufacturers (ODMs) and original equipment manufacturers (OEMs) for portable wireless routers (e.g., Mobile Router/MiFi), indoor and outdoor fixed wireless routers (e.g., CPE), industrial machine-to-machine (M2M) applications and smartphones.

We oversee sales, marketing, and accounting operations from our headquarters in San Jose, California. We conduct product design, development, and customer support through our fully owned subsidiaries, GCT Research, Inc. (GCT R) and MTH, Inc., both of which are located in South Korea. GCT R serves as our research and development center. In addition, we utilize separate sales offices for local technical support and sales in Taiwan, China, and Japan.

Our current product portfolio includes RF and modem chipsets based on 4th generation (4G), known as Long Term Evolution (LTE), technology offering a variety of chipsets differentiated by speed and functionality. These include 4G LTE, 4.5G LTE Advanced (twice the speed of LTE), and 4.75G LTE Advanced-Pro (four times the speed of LTE) chipsets. We also develop and sell cellular IoT chipsets for low-speed mobile networks such as eMTC/NB- IOT/Sigfox, and other network protocols.

*Corporate Information*

Our principal executive offices are located at 2290 North 1st Street, Suite 201 San Jose, CA 95131, and our telephone number is (408) 434-6040.

**Implications of Being a Smaller Reporting Company**

We are a smaller reporting company meaning that the market value of our Common Stock held by non-affiliates is less than $250.0 million measured on the last business day of our second fiscal quarter or our annual revenue is less than $100.0 million during the most recent completed fiscal year and the market value of our Common Stock held by non-affiliates is less than $700.0 million measured on the last business day of our second fiscal quarter. Accordingly, we may provide less public disclosure than larger public companies, including the inclusion of only two years of audited financial statements and only two years of management s discussion and analysis of financial condition and results of operations disclosure. As a result, the information that we provide to our stockholders may be different than you might receive from other public reporting companies in which you hold equity interests.

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**RISK FACTORS**

Investing in our securities involves risks. Before investing in our securities, you should carefully consider the specific risks set forth under the caption Risk Factors in our filings with the Securities and Exchange Commission (which we refer to as the SEC) that are incorporated by reference into this prospectus and under the caption Risk Factors in any accompanying prospectus supplement or free writing prospectus that we deliver to you. You should also carefully consider all other information contained in or incorporated by reference into this prospectus or in any accompanying prospectus supplement or free writing prospectus that we deliver to you. A discussion of the documents incorporated by reference into this prospectus is set forth below under the heading *Documents Incorporated by Reference*.

**** 

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**WHERE YOU CAN FIND MORE INFORMATION**

We are subject to certain information reporting requirements of the Securities Exchange Act of 1934, as amended (the Exchange Act), and, in accordance with these requirements, we file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are available to you at the SEC s website at http://www.sec.gov and our website at https://investors.gctsemi.com/sec-filings. The information contained in, or that can be accessed through, our website is not a part of this prospectus or any accompanying prospectus supplement.

We have filed with the SEC a registration statement on Form S-3 relating to the securities offered by this prospectus. This prospectus is a part of that registration statement, which includes additional information about us and the securities offered by this prospectus. You may review and obtain a copy of the registration statement and the exhibits that are a part of the registration statement through the SEC s website or our website. You can also call or write us for a copy as described below under *Documents Incorporated by Reference*.

**DOCUMENTS INCORPORATED BY REFERENCE**

The SEC allows us to incorporate by reference the information we file with the SEC under the Exchange Act, which means that we can disclose important information to you by referring you to those documents. Information incorporated by reference is considered to be a part of this prospectus, and information that we file later with the SEC will automatically update, modify and, where applicable, supersede this information. We incorporate by reference into this prospectus the specific documents listed below and all documents filed by us with the SEC pursuant to Section 13(a), 13(c), 14, or 15(d) of the Exchange Act between the date of this prospectus and the termination of the offering of securities under this prospectus (other than, in each case, documents or information deemed to be furnished and not filed in accordance with SEC rules), which future filings shall be deemed to be incorporated by reference into this prospectus and to be part of this prospectus from the date we subsequently file such documents. The SEC file number for these documents is 1-41013.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Our [Annual Report on Form 10-K for the fiscal year ended December 31, 2024, filed with the SEC on March 25, 2025](https://www.sec.gov/ix?doc=/Archives/edgar/data/1851961/000095017025044438/gcts-20241231.htm) ;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Our Current Reports on Form 8-K filed with the SEC on [January 29, 2025](https://www.sec.gov/ix?doc=/Archives/edgar/data/1851961/000092963825000430/form8k.htm) and [March 25, 2025](https://www.sec.gov/ix?doc=/Archives/edgar/data/1851961/000092963825001242/form8k.htm) (excluding any portions thereof that are furnished and not filed); and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The [description of our securities contained in Form 8-A/A filed with the Commission on April 5, 2024](https://www.sec.gov/Archives/edgar/data/1851961/000110465924043836/tm2411161d1_8a12ba.htm) .

Any statement contained in this prospectus or in any document incorporated by reference into this prospectus shall be deemed to be modified or, where applicable, superseded for the purposes of this prospectus to the extent that a statement contained in this prospectus or any subsequently filed document that also is incorporated by reference into this prospectus modifies or supersedes such prior statement. Any statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this prospectus.

We will provide to each person, including any beneficial owner, to whom a prospectus is delivered, upon written or oral request and without charge, a copy of the documents referred to above that we have incorporated by reference into this prospectus and a copy of the registration statement of which this prospectus is a part. You can request copies of such documents if you write us at our principal executive offices at 2290 North 1st Street, Suite 201 San Jose, CA 95131, or call our telephone number at (408) 434-6040.

Exhibits to the documents will not be sent, however, unless those exhibits have specifically been incorporated by reference into such document. You may also obtain copies of our SEC filings statement as described above under the heading *Where You Can Find More Information*.

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**CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS**

This prospectus, any accompanying prospectus supplement and the documents incorporated by reference herein and therein may contain forward-looking statements as defined by the Private Securities Litigation Reform Act of 1995. Our forward-looking statements include, but are not limited to, statements regarding our and our management team s expectations, hopes, beliefs, intentions or strategies regarding the future. In addition, any statements that refer to projections, forecasts or other characterizations of future events or circumstances, including any underlying assumptions, are forward-looking statements. The words anticipate, believe, continue, could, estimate, expect, intends, may, might, plan, possible, potential, predict, project, should, will, would and similar expressions may identify forward-looking statements, but the absence of these words does not mean that a statement is not forward-looking.

Forward-looking statements are not guarantees of performance. You should not put undue reliance on these statements which speak only as of the date hereof. You should understand that the following important factors, among others, could affect the Company s future results and could cause those results or other outcomes to differ materially from those expressed or implied in the Company s forward-looking statements:

<br> • our financial and business performance, including our financial projections and business metrics;

<br> • changes in our strategy, future operations, financial position, estimated revenues and losses, forecasts, projected costs, prospects and plans;

<br> • unexpected increases in our expenses resulting from inflationary pressures and rising interest rates, including manufacturing and operating expenses and interest expenses;

<br> • our inability to anticipate the future market demands and future needs of our customers;

<br> • our ability to develop new 5th generation (5G) products under collaboration agreements with our major partners;

<br> • the impact of component shortages, suppliers lack of production capacity, natural disasters or pandemics on our sourcing operations and supply chain;

<br> • our future capital requirements and sources and uses of cash;

<br> • our ability to obtain funding for our operations;

<br> • our anticipated financial performance, including gross margin, and the expectation that our future results of operations will fluctuate on a quarterly basis for the foreseeable future;

<br> • our expected capital expenditures, cost of revenue and other future expenses, and the sources of funds to satisfy our liquidity needs;

<br> • the outcome of any legal proceedings that may be instituted against us following completion of the Business Combination and transactions contemplated thereby;

<br> • our ability to maintain the listing of our Common Stock on the NYSE;

<br> • the risk that the Business Combination disrupts current plans and operations;

<br> • the ability to recognize the anticipated benefits of the Business Combination, which may be affected by, among other things, competition, and the ability of us to grow and manage growth profitably;

<br> • costs related to the Business Combination; and

<br> • other risks and uncertainties indicated in this prospectus, including those under Risk Factors herein, and other filings that have been made or will be made with the SEC.

&nbsp;&nbsp;&nbsp;&nbsp;<br>

These and other factors that could cause actual results to differ from those implied by the forward-looking statements in this prospectus are more fully described in the *Risk Factors* section. The risks described in Risk Factors are not exhaustive. These forward-looking statements are based on information available as of the date of this prospectus, and current expectations, forecasts and assumptions, and involve a number of judgments, risks and uncertainties. New risk factors emerge from time to time and it is not possible for us to predict all such risk factors, nor can we assess the impact of all such risk factors on our business or the extent to which any factor or combination of factors may cause actual results to differ materially from those contained in any forward-looking statements. All forward-looking statements attributable to us or persons acting on our behalf are expressly qualified in their entirety by the foregoing cautionary statements. We undertake no obligations to update or revise publicly any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law.

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**USE OF PROCEEDS**

Unless we inform you otherwise in the prospectus supplement or a free writing prospectus, we intend to use the net proceeds from the sale of the securities for general corporate purposes, including, but not limited to, working capital, capital expenditures, repayment of indebtedness, investments in our subsidiaries, business acquisitions and the repurchase, redemption or retirement of our securities, including shares of our common stock. We may also invest the net proceeds in U.S. government securities, certificates of deposit or other interest-bearing securities. If we decide to use the net proceeds from a particular offering of securities for a specific purpose, we will describe that in the prospectus supplement relating to that offering.

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**DESCRIPTION OF COMMON STOCK**

 

*The following summary of the material terms of our securities is not intended to be a complete summary of the rights and preferences of such securities. The descriptions below are qualified by reference to the actual text of our Second Amended and Restated Certificate of Incorporation (our Charter). We urge you to read our Charter in its entirety for a complete description of the rights and preferences of our securities.*

 

***Authorized and Outstanding Capital Stock***

Our Charter authorizes the issuance of 400,000,000 shares of Common Stock, $0.0001 par value per share and 40,000,000 shares of Preferred Stock, $0.0001 par value.

As of March 20, 2025, there were 48,246,480 shares of Common Stock issued and outstanding and no shares of Preferred Stock issued and outstanding.

***Voting Power***

Except as otherwise provided by the General Corporate Law of the State of Delaware (the DGCL) or our Charter and subject to the rights of holders of any series of Preferred Stock, all of the voting power of our stockholders will be vested in the holders of our Common Stock, and each holder of our Common Stock will have one vote for each share held by such holder on all matters voted upon by the stockholders of the Company; provided, however, that, except as otherwise required by law, holders of our Common Stock, as such, will not be entitled to vote on any amendment to our Charter (or on any amendment to a certificate of designations of any series of Preferred Stock) that alters or changes the powers, preferences, rights or other terms of one or more outstanding series of Preferred Stock if the holders of such affected series of Preferred Stock are entitled to vote, either separately or together with the holders of one or more other such series, on such amendment pursuant to our Charter (or pursuant to a certificate of designations of any series of Preferred Stock) or pursuant to the DGCL. There will be no cumulative voting.

***Dividends***

Except as otherwise provided by the DGCL or our Charter, dividends may be declared and paid on our Common Stock from funds lawfully available therefor if, as and when determined by our Board and subject to any preferential dividend rights of any then outstanding shares of Preferred Stock.

***Liquidation***

Upon the dissolution or liquidation or winding up of the affairs of the Company, whether voluntary or involuntary, holders of our Common Stock will be entitled to receive all our assets available for distribution to our stockholders equally on a per share basis, subject to any preferential rights of any then outstanding shares of Preferred Stock and after payment or provision for payment of our debts.

***Preemptive Rights; Redemption Rights***

The holders of our Common Stock will have no preemptive rights to subscribe for any shares of any class of our stock. Our Common Stock will not be convertible into, or exchangeable for, shares of any other class or classes or of any other series of the same class of our capital stock.

***Listing***

Our Common Stock and our Warrants are currently listed on the NYSE under the symbols GCTS and GCTS-WT, respectively.

***Transfer Agent and Registrar***

The transfer agent and registrar for our Common Stock is Continental Stock Transfer & Trust Company.

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**DESCRIPTION OF PREFERRED STOCK**

Our Charter provides that shares of our Preferred Stock may be issued from time to time in one or more series. Our Board will be authorized to establish the voting rights, if any, designations, preferences and relative, participating, optional or other special rights of the shares of such series, and the qualifications, limitations or restrictions thereof, applicable to the shares of each series of our Preferred Stock. Our Board can, without stockholder approval, issue our Preferred Stock with voting and other rights that could adversely affect the voting power and other rights of the holders of our Common Stock and could have anti-takeover effects. The ability of our Board to issue our Preferred Stock without stockholder approval could have the effect of delaying, deferring or preventing a change of control or the removal of existing management. We have no Preferred Stock outstanding at the date hereof.

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**DESCRIPTION OF WARRANTS**

 

*The following summarizes the general terms of stock and debt warrants that we may offer. The particular terms of any stock and debt warrants will be described in an accompanying prospectus supplement. The description below and in any accompanying prospectus supplement is not complete. You should read the form of warrant agreement and any warrant certificate that we will file with the SEC.*

**Warrants to Purchase Capital Stock**

If we offer stock warrants, the prospectus supplement will describe the terms of the stock warrants, including:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The offering price, if any;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• If applicable, the designation and terms of any Preferred Stock purchasable upon exercise of Preferred Stock warrants;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The number of shares of Common Stock or Preferred Stock purchasable upon exercise of one stock warrant and the initial price at which the shares may be purchased upon exercise;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The dates on which the right to exercise the stock warrants begins and expires;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• U.S. federal income tax consequences;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Call provisions, if any;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The currencies in which the offering price and exercise price are payable; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• If applicable, the antidilution provisions of the stock warrants.

The shares of Common Stock or Preferred Stock we issue upon exercise of the stock warrants will, when issued in accordance with the stock warrant agreement, be validly issued, fully paid and nonassessable.

**Exercise of Warrants to Purchase Capital Stock**

You may exercise stock warrants by surrendering to the stock warrant agent the stock warrant certificate, which indicates your election to exercise all or a portion of the stock warrants evidenced by the certificate. Surrendered stock warrant certificates must be accompanied by payment of the exercise price in the form of cash or check. The stock warrant agent will deliver certificates evidencing duly exercised stock warrants to the transfer agent. Upon receipt of the certificates, the transfer agent will deliver a certificate representing the number of shares of Common Stock or Preferred Stock purchased. If you exercise fewer than all the stock warrants evidenced by any certificate, the stock warrant agent will deliver a new stock warrant certificate representing the unexercised stock warrants.

**No Rights as Stockholders**

Holders of stock warrants are not entitled to vote, to consent, to receive dividends or to receive notice as stockholders with respect to any meeting of stockholders or to exercise any rights whatsoever as our stockholders.

**Warrants to Purchase Debt Securities**

If we offer debt warrants, the accompanying prospectus supplement will describe the terms of the warrants, including:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The offering price, if any;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The designation, aggregate principal amount and terms of the debt securities purchasable upon exercise of the warrants and the terms of the indenture under which the debt securities will be issued;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• If applicable, the designation and terms of the debt securities with which the debt warrants are issued and the number of debt warrants issued with each debt security;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• If applicable, the date on and after which the debt warrants and the related securities will be separately transferable;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The principal amount of debt securities purchasable upon exercise of one debt warrant, and the price at which the principal amount of debt securities may be purchased upon exercise;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The dates on which the right to exercise the debt warrants begins and expires;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• U.S. federal income tax consequences;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Whether the warrants represented by the debt warrant certificates will be issued in registered or bearer form;

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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The currencies in which the offering price and exercise price are payable; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• If applicable, any antidilution provisions.

You may exchange debt warrant certificates for new debt warrant certificates of different denominations and may present debt warrant certificates for registration of transfer at the corporate trust office of the debt warrant agent, which will be listed in an accompanying prospectus supplement.

**Exercise of Warrants to Purchase Debt Securities**

You may exercise debt warrants by surrendering the debt warrant certificate at the corporate trust office of the debt warrant agent, with payment in full of the exercise price. Upon the exercise of debt warrants, the debt warrant agent will, as soon as practicable, deliver the debt securities in authorized denominations in accordance with your instructions and at your sole cost and risk. If less than all the debt warrants evidenced by the debt warrant certificate are exercised, the agent will issue a new debt warrant certificate for the remaining amount of debt warrants.

**No Rights as Holders of Debt Securities**

Warrant holders do not have any of the rights of holders of debt securities, except to the extent that the consent of warrant holders may be required for certain modifications of the terms of an indenture or form of the debt security, as the case may be, and the series of debt securities issuable upon exercise of the debt warrants. In addition, warrant holders are not entitled to payments of principal of and interest, if any, on the debt securities.

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**DESCRIPTION OF DEBT SECURITIES**

**General**

We may issue debt securities either separately, or together with, or upon the conversion or exercise of or in exchange for, other securities described in this prospectus. Debt securities may be our senior, senior subordinated or subordinated obligations and may be issued in one or more series. Unless otherwise expressly stated in an accompanying prospectus supplement, the debt securities will represent our general, unsecured obligations and will rank equally with all of our other unsecured indebtedness.

Any debt securities that we issue will be issued under an indenture that will be entered into between us and a bank or trust company, or other trustee that is qualified to act under the Trust Indenture Act of 1939 (the TIA), which we select to act as trustee. A copy of the indenture (the Indenture) will be filed as an exhibit to a prospectus supplement to the registration statement of which this prospectus forms a part. The Indenture may be modified by one or more supplemental indentures, which we will incorporate by reference as an exhibit to the registration statement of which this prospectus is a part. Any debt securities that we issue will include those stated in the Indenture (including any supplemental indentures that specify the terms of a particular series of debt securities) as well as those made part of the Indenture by reference to the TIA, as in effect on the date of the Indenture. The Indenture will be subject to and governed by the terms of the TIA.

The following description and any description in an accompanying prospectus supplement is a summary only and is subject to, and qualified in its entirety by reference to the terms and provisions of the indentures and any supplemental indentures that we file with the SEC in connection with an issuance of any series of debt securities. You should read all of the provisions of the Indentures, including the definitions of certain terms, as well as any supplemental indentures that we file with the SEC in connection with the issuance of any series of debt securities. These summaries set forth certain general terms and provisions of the securities to which any accompanying prospectus supplement may relate. The specific terms and provisions of a series of debt securities and the extent to which the general terms and provisions may also apply to a particular series of debt securities will be described in the accompanying prospectus supplement. Copies of the Indenture may be obtained from us or the Trustee.

Please read the accompanying prospectus supplement relating to the series of debt securities being offered for specific terms including, when applicable:

<br> • the title of the debt securities of the series;

• the price or prices (expressed as a percentage of the principal amount thereof) at which debt securities of the series will be issued;

• any limit on the aggregate principal amount of that series of debt securities;

<br> • whether such securities rank as senior debt securities, senior subordinated debt securities or subordinated debt securities;

<br> • the terms and conditions, if any, upon which the debt securities of the series shall be exchanged for or converted into other of our securities or securities of another person;

<br> • if the debt securities of there will be secured by any collateral and, if so, a general description of the collateral and the terms and provisions of such collateral security, pledge or other agreements;

<br> • the date or dates on which we will pay the principal of the debt securities of the series;

• the rate or rates, which may be fixed or variable, at which debt securities of the series will bear interest, if any, or the method or methods, if applicable, used to determine those rates, the date or dates, if any, from which interest on the debt securities of the series will begin to accrue, or the method or methods, if any, used to determine those dates, the dates on which the interest, if any, on the debt securities of the series will be payable and the record dates for the payment of interest;

• the manner in which the amounts of payment of principal of or interest, if any, of the debt securities of the series will be determined, if such amounts may be determined by reference to an index based on a currency or currencies or by reference to a currency exchange rate, commodity, commodity index, stock exchange index or financial index;

• if other than the corporate trust office of the Trustee, the place or places where amounts due on the debt securities of the series will be payable and where the debt securities of the series may be surrendered for registration of transfer and exchange and where notices and demands to or upon us in respect of the debt securities of the series may be served, and the method of such payment, if by wire transfer, mail or other means;

<br> • if applicable, the period or periods within which, and the terms and conditions upon which, we may, at our option, redeem debt securities of the series;

<br> • the terms and conditions, if applicable, upon which the holders of debt securities may require us to repurchase or redeem debt securities of the series at the option of the holders of debt securities of the series;

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<br> • the provisions, terms and conditions, if any, with respect to any sinking fund or analogous provision;

• the authorized denominations in which the debt securities of the series will be issued, if other than denominations of $1,000 and any integral multiples of $1,000 in excess thereof;

<br> • whether the debt securities of the series are to be issuable, in whole or in part, in bearer form;

<br> • whether any fully regulated debt securities of the series will be issued in temporary or permanent global form (global debt securities) and, if so, the identity of the depositary for the global debt securities if other than The Depository Trust Company;

<br> • any depositaries, interest rate calculation agents, exchange rate calculation agents or other agents;

<br> • the trustee for the debt securities;

• the portion of the principal amount of the debt securities of the series which will be payable upon acceleration of maturity, if other than the full principal amount;

<br> • any addition to, or modification or deletion of, any covenant described in this prospectus or in the Indenture;

<br> • any events of default, if not otherwise described below under Events of Default and any change to the right of the holders to declare the principal of any debt securities due and payable;

• if other than U.S. dollars, the currency, currencies or currency units of denomination of the debt securities of the series, which may be any foreign currency, and if such currency denomination is a composite currency, the agency or organization, if any, responsible for overseeing such composite currency;

• if other than U.S. dollars, the currency, currencies or currency units in which the purchase price for the debt securities of the series will be payable, in which payments of principal and, if applicable, premium or interest on the debt securities of the series will be payable, and, if necessary, the manner in which the exchange rate with respect to such payments will be determined;

<br> • any listing of the debt securities on any securities exchange;

<br> • any additions or deletions to the defeasance or the satisfaction and discharge provisions set forth herein;

• if and under what circumstances we will pay additional amounts (Additional Amounts) on the debt securities of the series in respect of specified taxes, assessments or other governmental charges and, if so, whether we will have the option to redeem the debt securities of the series rather than pay the Additional Amounts;

<br> • the priority and kind of any lien securing the debt securities and a brief identification of the principal properties subject to such lien;

<br> • additions or deletions to or changes in the provisions relating to modification of any Indenture; and

<br> • any other terms of the debt securities of the series (whether or not such other terms are consistent or inconsistent with any other terms of the Indenture).

As used in this prospectus and any accompanying prospectus supplement relating to the offering of debt securities of any series, references to the principal of and premium, if any, and interest, if any, on the debt securities of the series include the payment of Additional Amounts, if any, required by the debt securities of the series to be paid in that context.

Debt securities may be issued as original issue discount securities to be sold at a substantial discount below their principal amount. In the event of an acceleration of the maturity of any original issue discount security, the amount payable to the holder upon acceleration will be determined in the manner described in the accompanying prospectus supplement. Certain U.S. federal income tax considerations applicable to original issue discount securities will be described in any accompanying prospectus supplement.

If the purchase price of any debt securities is payable in a foreign currency or if the principal of, or premium, if any, or interest, if any, on any debt securities is payable in a foreign currency, the specific terms of those debt securities and the applicable foreign currency will be specified in the accompanying prospectus supplement relating to those debt securities.

The terms of the debt securities of any series may differ from the terms of the debt securities of any other series, and the terms of particular debt securities within any series may differ from each other. Unless otherwise expressly provided in the accompanying prospectus supplement relating to any series of debt securities, we may, without the consent of the holders of the debt securities of any series, reopen an existing series of debt securities and issue additional debt securities of that series.

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Unless otherwise described in an accompanying prospectus supplement relating to any series of debt securities, there will be no limitation upon our ability to incur indebtedness or other liabilities or that would afford holders of debt securities protection in the event of a business combination, takeover, recapitalization or highly leveraged or similar transaction involving us. Accordingly, we may in the future enter into transactions that could increase the amount of our consolidated indebtedness and other liabilities or otherwise adversely affect our capital structure or credit rating without the consent of the holders of the debt securities of any series.

**Registration, Transfer and Payment**

Unless otherwise indicated in the applicable prospectus supplement, each series of debt securities will be issued in registered form only, without coupons.

Unless otherwise indicated in the applicable prospectus supplement, debt securities will be issued in denominations of $1,000 or any integral multiples of $1,000 in excess thereof.

Unless otherwise indicated in the accompanying prospectus supplement, the debt securities will be payable and may be surrendered for registration of transfer or exchange and, if applicable, for conversion into or exchange for other securities or property, at an office or agency maintained by us in the United States. However, we may, at our option, make payments of interest on any registered debt security by check mailed to the address of the person entitled to receive that payment or by wire transfer to an account maintained by the payee with a bank located in the United States. Unless otherwise indicated in the accompanying prospectus supplement, no service charge shall be made for any registration of transfer or exchange, redemption or repayment of debt securities, or for any conversion or exchange of debt securities for other securities or property, but we may require payment of a sum sufficient to cover any tax or other governmental charge that may be imposed in connection with that transaction.

Unless otherwise indicated in the applicable prospectus supplement, we will not be required to:

• issue, register the transfer of or exchange debt securities of any series during a period beginning at the opening of business 15 days before any mailing of a notice of a redemption for the debt securities of that series selected for redemption and ending at the close of business on the day of such mailing; or

<br> • register the transfer of or exchange any debt security, or portion of any debt security, selected for redemption, except the unredeemed portion of any registered debt security being redeemed in part.

**Book-Entry Debt Securities**

We may issue the debt securities in whole or in part in the form of one or more global certificates or notes, which we refer to as global securities, that we will deposit with a depository or its nominee that we identify in the applicable prospectus supplement.

We will describe the specific terms of the depository arrangement covering the debt securities in the prospectus supplement relating to that series. We anticipate that the following provisions will apply to all depository arrangements.

Upon the issuance of the debt securities in the form of one or more global securities, the depository or its custodian will credit, on its book-entry registration and transfer system, the number of shares or principal amount of securities of the individual beneficial interests represented by these global securities to the respective accounts of persons who have accounts with the depository. Ownership of beneficial interests in the global securities will be shown on, and the transfer of this ownership will be effected only through, records maintained by the depository or its nominee with respect to interests of participants and the records of participants with respect to interests of persons other than participants. These accounts initially will be designated by or on behalf of the underwriters, initial purchasers or agents, or by us if we offer and sell the debt securities directly, and ownership of beneficial interests in the global securities will be limited to participants or persons who hold interests through participants. Qualified institutional buyers may hold their interests in the global securities directly through the depository if they are participants in this system, or indirectly through organizations which are participants in this system. The laws of some states of the U.S. may require that some purchasers of securities take physical delivery of the debt securities in definitive registered form. These limits and the laws may impair your ability to own, transfer or pledge interests in the global securities.

So long as the depository, or its nominee, is the registered owner or holder of the debt securities, the depository or its nominee, as the case may be, will be considered the sole owner or holder of the debt securities represented by the global securities for all purposes. No beneficial owner of an interest in the global securities will be able to transfer that interest except in accordance with the depository s procedures.

We will make dividend payments on, or payments of the principal of, and premium, if any, and interest on, the global securities to the depository or its nominee, as the case may be, as the registered owner of the global securities. We will not have any responsibility or liability for any aspect of the records relating to or payments made on account of beneficial ownership interests in the global securities or for maintaining, supervising or reviewing any records relating to the beneficial ownership interest.

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We expect that the depository or its nominee, upon receipt of any dividend payment on, or payment of the principal of, and premium, if any, and interest on, the global securities, will credit participants accounts with payments in amounts proportionate to their respective beneficial interests in the debt securities as shown on the records of the depository or its nominee. We also expect that payments by participants to owners of beneficial interests in the global securities held through the participants will be governed by standing instructions and customary practice, as is now the case with securities held for the accounts of customers registered in the names of nominees for their customers. These payments will be the responsibility of the participants. Transfers between participants in the depository will be effected in the ordinary way through the depository s settlement system in accordance with the depository rules and will be settled in same day funds.

We will issue securities in certificated form in exchange for global securities (subject, in the case of the third bullet point, to the procedures of the depository) if:

<br> • the depository notifies us that it is unwilling or unable to continue as a depository for the global securities or ceases to be a clearing agency registered under the Exchange Act of 1934, and a successor depository is not appointed by us within 90 days of the notice;

<br> • an event of default under the instrument governing the debt securities has occurred and is continuing; or

<br> • we determine that the debt securities will no longer be represented by the global securities.

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**DESCRIPTION OF RIGHTS**

As specified in the applicable prospectus supplement, we may issue rights to purchase the securities offered in this prospectus to our existing stockholders, and such rights may or may not be issued for consideration. The applicable prospectus supplement will describe the terms of any such rights. The description in the prospectus supplement will not purport to be complete and will be qualified in its entirety by reference to the documents pursuant to which such rights will be issued.

**DESCRIPTION OF UNITS**

As may be specified in an accompanying prospectus supplement, we may issue units consisting of one or more of our securities registered hereby. An accompanying prospectus supplement will describe:

<br> • the terms of the units and of the securities comprising the units, including whether and under what circumstances the securities comprising the units may be traded separately;

<br> • a description of the terms of any unit agreement governing the units; and

<br> • a description of the provisions for the payment, settlement, transfer or exchange of the units.

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**PLAN OF DISTRIBUTION**

We may offer and sell the securities under this prospectus from time to time in one or more of the following ways:

<br> • through agents;

<br> • to dealers;

<br> • to underwriters;

<br> • directly to other purchasers or investors; or

<br> • through a combination of any of these methods of sale.

The distribution of the securities may be made from time to time in one or more transactions, either:

<br> • at a fixed price or prices, which may be changed;

<br> • at market prices prevailing at the time of sale;

<br> • at prices related to prevailing market prices;

<br> • at prices determined by an auction process; or

<br> • at negotiated prices.

**Through Agents**

We and the agents designated by us may solicit offers to purchase securities. Agents that participate in the distribution of securities may be deemed underwriters under the Securities Act of 1933, as amended (which we refer to as the Securities Act). Any agent will be acting on a best efforts basis for the period of its appointment, unless we indicate differently in the prospectus supplement.

**To Dealers**

The securities may be sold to a dealer as principal. The dealer may then resell the securities to the public at varying prices determined by it at the time of resale. The dealer may be deemed to be an underwriter under the Securities Act.

**To Underwriters**

We may sell securities to one or more underwriters under an underwriting agreement that we enter into with them at the time of sale. The names of the underwriters will be set forth in the prospectus supplement, which will be used by the underwriters to resell the securities.

In addition, we may enter into derivative transactions with third parties, or sell securities not covered by this prospectus to third parties in privately negotiated transactions. If the applicable prospectus supplement indicates, in connection with such a transaction, that the third parties may sell securities covered by this prospectus and the applicable prospectus supplement, including in short sale transactions. If so, the third party may use securities pledged by us or borrowed from us or others to settle such sales or to close out any related open borrowings of stock, and may use securities received from us in settlement of a derivative transaction to close out any related open borrowings of stock. We otherwise may loan or pledge securities to a financial institution or other third party that in turn may sell the loaned securities or, in an event of default in the case of a pledge, sell the pledged securities, in either case using this prospectus and the applicable prospectus supplement.

**Direct Sales**

We may sell securities directly to you, without the involvement of underwriters or agents.

**General Information**

Any underwriters or agents will be identified and their compensation described in the prospectus supplement applicable to such offering.

We may have agreements with the underwriters, dealers and agents to indemnify them against certain civil liabilities, including liabilities under the Securities Act, or to contribute to payments they may be required to make.

Underwriters, dealers and agents (or one or more of their respective affiliates) may engage in transactions with, or perform services for, us or our subsidiaries in the ordinary course of their businesses.

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**LEGAL MATTERS**

Unless otherwise indicated in the applicable prospectus supplement, the validity of the securities offered by this prospectus will be passed upon for us by Morgan, Lewis & Bockius LLP, Palo Alto, California, and for any underwriters or agents by counsel named in the applicable prospectus supplement.

**EXPERTS**

The consolidated financial statements of the Company as of December 31, 2024 and 2023, and for each of the two years in the period ended December 31, 2024, incorporated in this registration statement by reference to the [Annual Report on Form 10-K for the year ended December 31, 2024](https://www.sec.gov/ix?doc=/Archives/edgar/data/1851961/000095017025044438/gcts-20241231.htm), have been so incorporated in reliance on the report (which contains an explanatory paragraph relating to the Company s ability to continue as a going concern as described in Note 1 to the consolidated financial statements) of BPM LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

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### GCT Semiconductor Holding, Inc.

### <sub>Up to $120,000,000 of Common Stock</sub>
_________________________________________ <br>

#### PROSPECTUS SUPPLEMENT
_________________________________________ <br>

B. Riley Securities H.C. Wainwright & Co.

_________________________________________

#### June 18, 2026
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