Company: KELYB
Filing Date: 2025-12-12
Form Type: 8-K/A
Source: 0001193125-25-317582
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Company: KELLY SERVICES INC
Filing Date: 2025-12-12
Form: 8-K/A
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UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K/A (Amendment No. 1) CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): November 12, 2025 KELLY SERVICES, INC. (Exact Name of Registrant as Specified in its Charter)

| DELAWARE                                       |     | 000-01088               |     | 38-1510762            |
| (State or Other Jurisdiction of Incorporation) |     | -Commission File Number |     | -IRS Employer         
 Identification Number |

999 WEST BIG BEAVER ROAD TROY, MICHIGAN 48084 (Address of Principal Executive Offices) (Zip Code) (248) 362-4444 (Registrant’s Telephone Number, Including Area Code) Check the appropriate box below if the Form 8-Kfiling is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

| ☐ | Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) |

| ☐ | Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) |

| ☐ | Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) |

| ☐ | Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c)) |

Securities registered pursuant to Section 12(b) of the Act:

| Title of Each Class                             |     | Trading 
 Symbol  |     | Name of Each Exchange on Which Registered |
| Class A Common Stock, $1.00 par value per share |     | KELYA   |     | The Nasdaq Stock Market LLC               |
| Class B Common Stock, $1.00 par value per share |     | KELYB   |     | The Nasdaq Stock Market LLC               |

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2of the Securities Exchange Act