In the Original Investigation titled “Effects of Psilocybin-Assisted Therapy on Major Depressive Disorder: A Randomized Clinical Trial,”1 published online on November 4, 2020, there was an error in the response rate for the overall sample, which was marginally higher than reported (67% should have been 71%), and errors in several Cohen d and 95% CI values in the Abstract Results, Results section, and captions for Figures 3 and 4. There are additional corrections in eTables 1 and 2 and eFigures 1 to 9 in the Supplement. A Letter of Explanation2 has been published that explains the errors. This article was corrected online.