Company: TEM
Filing Date: 2025-08-08
Form Type: S-3ASR
Source: 0001193125-25-175993
Chunk: 1

Company: Tempus AI, Inc.
Filing Date: 2025-08-08
Form: S-3ASR
Chunk 1
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 Rule 462(e) under the Securities Act, check the following box. ☒ If this Form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box. ☐ Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-acceleratedfiler, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2of the Exchange Act.

| Large accelerated filer |     | ☐ |     | Accelerated filer         |     | ☐ |
| Non-accelerated filer   |     | ☒ |     | Smaller reporting company |     | ☐ |
|                         |     |   |     | Emerging growth company   |     | ☒ |

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

EXPLANATORY NOTE This registration statement contains three prospectuses:

| • |     | a base prospectus that covers the offering, sale and issuance by us of the securities identified in the base 
 prospectus from time to time in one or more offerings (the “Base Prospectus”);                               |

| • |     | a prospectus that covers the offering and sale by selling stockholders of Class A common stock from time to 
 time (the “Selling Stockholder Prospectus”); and                                                            |

| • |     | a sales agreement prospectus, which covers the offering, sale and issuance by us of up to a maximum aggregate                                                                           
 offering price of $500,000,000 of our Class A common stock that may be issued and sold from time to time under a Controlled Equity OfferingSM sales agreement with Morgan Stanley & Co. 
 LLC, Cantor Fitzgerald & Co., TD Securities (USA) LLC and Allen & Company LLC (the “ATM Prospectus”).                                                                                   |

The Base Prospectus immediately follows this explanatory note. The specific terms of any securities to be offered pursuant to the Base Prospectus will be specified in one or more prospectus supplements to the Base Prospectus