Company: AAOI
Filing Date: 2025-11-07
Form Type: 424B5
Source: 0001104659-25-108494
Chunk: 7

Company: APPLIED OPTOELECTRONICS, INC.
Filing Date: 2025-11-07
Form: 424B5
Chunk 7
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 page S-9 of this prospectus supplement.

#### Nasdaq Global Market symbol
AAOI

#### Risk factors
Investing in our common stock involves significant risks. Please see “Risk Factors” beginning on page S-5 of this prospectus supplement, page 2 of the accompanying base prospectus and in the documents incorporated by reference herein, to read about factors you should consider before deciding to purchase shares of our common stock.

(1)

Based on shares outstanding as of November 6, 2025, excluding the following shares of common stock reserved for issuance as of that date:

•

restricted stock units representing a total of 1,482,851 shares of common stock issuable upon vesting;

•

performance stock units representing a total of 1,188,826 shares of common stock issuable upon the satisfaction of performance-based vesting conditions that were outstanding as of November 6, 2025;

•

any shares issuable upon conversion of our 2.75% Convertible Senior Notes due 2030; and

•

any shares issuable upon exercise of warrants issued to Amazon.com, Inc.

<div align='center'>S-4</div>

TABLE OF CONTENTS

### RISK FACTORS
An investment in our common stock involves a high degree of risk. You should consider carefully the risks described below and discussed under the section captioned “Risk Factors” contained in our most recent Annual Report on Form 10-K, as revised or supplemented by our Quarterly Reports on Form 10-Q since the filing of our most recent Annual Report on Form 10-K, each of which is incorporated by reference in this prospectus supplement in their entirety, together with other information in this prospectus supplement, and the information and documents incorporated by reference in this prospectus supplement, the accompanying base prospectus and any free writing prospectus with respect to this offering filed by us with the SEC, before you make a decision to invest in our common stock. The risks and uncertainties described below are not the only ones we face. Other risks and uncertainties, including those that we do not currently consider material, may impair our business. If any of these risks actually occur, our business, financial condition, operating results or cash flows could be materially adversely affected. This could cause the trading price of our common stock to decline, resulting in a loss of all or part of your investment.

The common stock offered under this prospectus supplement and the accompanying base prospectus may be sold in “at-the-market” offerings, and investors who buy shares at