Filed Pursuant to Rule 424(b)(3)
Registration No. 333-264243
Prospectus Supplement No. 1
(to Prospectus dated April 26, 2022)
ATI Physical Therapy, Inc.
9,807,085 shares of Common Stock
11,498,401 Warrants
Up
to 11,498,401 shares of Common Stock Issuable upon Exercise of the Warrants
This prospectus
supplement updates and supplements the prospectus dated April 26, 2022 (the Prospectus), which forms a part of our registration statement on Form S-1 (No. 333-264243). This prospectus supplement is being filed to update and supplement
the information in the Prospectus with information contained in our Quarterly Report on Form 10-Q, filed with the Securities and Exchange Commission on May 10, 2022 (the Quarterly Report). Accordingly, we have attached the Quarterly
Report to this prospectus supplement.
This Prospectus and this prospectus supplement relate to: (1) the issuance by us of up to 5,226,546
shares of Class A common stock, par value $0.0001 per share (Common Stock), of ATI Physical Therapy, Inc., a Delaware corporation (the Company, we, our) that may be issued upon exercise of
warrants at an exercise price of $3.00 per share (the Series I Warrants), (2) the issuance by us of up to 6,271,855 shares of Common Stock issuable upon the exercise of warrants at an exercise price of $0.01 per share (Series
II Warrants and together with the Series I Warrants, the Warrants), (3) the offer and sale from time to time by the selling securityholders identified in the Prospectus (the Selling Securityholders), or their
permitted transferees, of up to 9,807,085 shares of Common Stock currently outstanding and 11,498,401 Warrants.
Our Common Stock and our
Public Warrants (as such term is defined in the Prospectus under Selected Definitions) are listed on the New York Stock Exchange under the symbol ATIP and ATIPWS, respectively. On May 12, 2022, the last
reported sales prices of our Common Stock was $1.56 per share and the last reported sales price of our Public Warrants was $0.18 per warrant.
This prospectus supplement updates and supplements the information in the Prospectus, including any amendments or supplements thereto, and is
not complete without, and may not be delivered or utilized except in combination with, the Prospectus, including any subsequent amendments or supplements thereto. This prospectus supplement should be read in conjunction with the Prospectus,
including any amendments or supplements thereto, and if there is any inconsistency between the information in the Prospectus, any prior amendments or supplements thereto, and this prospectus supplement, you should rely on the information in this
prospectus supplement. The information in this prospectus supplement modifies and supersedes, in part, the information in the Prospectus, including any amendments or supplements thereto. Any information in the Prospectus or any prior amendments or
supplements thereto, that is modified or superseded shall not be deemed to constitute a part of the Prospectus except as modified or superseded by this prospectus supplement. You should not assume that the information provided in this prospectus
supplement, the Prospectus or any prior amendments or supplements thereto, is accurate as of any date other than their respective dates. Neither the delivery of this prospectus supplement, the Prospectus, any prior amendments or supplements thereto,
nor any sale made hereunder, shall under any circumstances create any implication that there has been no change in our affairs since the date of this prospectus supplement, or that the information contained in this prospectus supplement, the
Prospectus or any prior amendments or supplements thereto, is correct as of any time after the date of that information.
Investing in
our Common Stock involves a high degree of risk. See Risk Factors beginning on page 10 of the Prospectus.
Neither the
Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities, or determined if this prospectus supplement is truthful or complete. Any representation to the contrary is a criminal offense.
The date of this prospectus supplement is May 13, 2022