Company: SFNC
Filing Date: 2025-07-23
Form Type: 424B5
Source: 0001193125-25-162761
Chunk: 0

Company: SIMMONS FIRST NATIONAL CORP
Filing Date: 2025-07-23
Form: 424B5
Chunk 0
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Filed Pursuant to Rule 424(b)(5)
Registration No. 333-279502 PROSPECTUS SUPPLEMENT (To Prospectus dated May 17, 2024) 16,220,000 Shares Simmons First National Corporation Class A Common Stock We are offering 16,220,000 shares of our Class A common stock, par value $0.01 per share, or our common stock. Our common stock is listed on the Nasdaq Global Select Market (“Nasdaq”) under the symbol “SFNC.” The last reported closing price of our common stock on Nasdaq on July 18, 2025 was $20.06 per share. Investing in our common stock involves certain risks. Please read the “ Risk Factors” beginning on page S-16of this prospectus supplement, on page 4 of the accompanying prospectus and contained in our Annual Report on Form 10-Kfor the year ended December 31, 2024 (the “Annual Report”), which is incorporated herein by reference, as well as the risks set forth in our other filings with the U.S. Securities and Exchange Commission (“SEC”) that are incorporated by reference herein, for a discussion of certain risks that should be considered in connection with an investment in our common stock.

|                                  |     | Per Share |         |     | Total(1) |                |
|:---------------------------------|:----|:----------|--------:|:----|:---------|---------------:|
| Public offering price            |     | $         |   18.50 |     | $        | 300,070,000.00 |
| Underwriting discounts and       
 commissions(2)                   |     | $         |  0.9250 |     | $        |  15,003,500.00 |
| Proceeds, before expenses, to us |     | $         | 17.5750 |     | $        | 285,066,500.00 |

| (1) | Assumes (i) no exercise of the underwriters’ option to purchase additional shares described below and           
 (ii) no participation in the directed share program for purposes of the underwriting discounts and commissions. |

| (2) | Represents underwriting discounts and commissions equal to five percent (5%) per share, which is the                                                                                                                                                    
 underwriting discount we have agreed to pay on shares sold in this offering to investors introduced by the underwriters. For shares sold in this offering pursuant to the directed share program,