Company: HCKT
Filing Date: 2025-11-04
Form Type: SC TO-C
Source: 0001193125-25-265008
Chunk: 0

Company: HACKETT GROUP, INC.
Filing Date: 2025-11-04
Form: SC TO-C
Chunk 0
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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K 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 4, 2025 The Hackett Group, Inc. (Exact name of registrant as specified in its charter)

| FLORIDA                         |     | 333-48123   |     | 65-0750100         |
| (State or other jurisdiction of 
 incorporation or organization)  |     | -Commission 
 File Number |     | -I.R.S. Employer   
 Identification No. |

| 1001 Brickell Bay Drive, Suite 3000      
 Miami, Florida                           |     |     33131 |
| (Address of principal executive offices) |     | -Zip Code |

(305) 375-8005 (Registrant’s telephone number, including area code) Not Applicable (Former name or former address, if changed since last report) 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(s) |     | Name of each exchange 
 on which registered   |
| Common Stock, par value $.001 per share |     | HCKT      |     | NASDAQ Stock Market   |

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR § 230.405) or Rule 12b-2of the Securities Exchange Act of 1934 (17 CFR §