Background: A recent epidemiological study suggested that 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT) used for spiritual and recreational reasons is associated with subjective improvement in depression and anxiety. Further exploration of the potential psychotherapeutic effects of 5-MeO-DMT could inform future clinical trials. Objectives: We examined self-reported improvement in depression and anxiety among people who use 5-MeO-DMT in a group setting with structured procedures guiding dose and administration of 5-MeO-DMT. Such procedures also include activities for the preparation of, and support during/following sessions, which are similar to procedures used in clinical trials of hallucinogen administration. Next, we examined whether depression or anxiety were improved following use, and whether the acute subjective effects (mystical/challenging) or beliefs about the 5-MeO-DMT experience were associated with improvements in these conditions. Methods: Respondents (n = 362; Mage = 47.7; Male = 55%; White/Caucasian = 84%) completed an anonymous web-based survey. Results: Of those reporting having been diagnosed with depression (41%) or anxiety (48%), most reported these conditions were improved (depression = 80%; anxiety = 79%) following 5-MeO-DMT use, and fewer reported they were unchanged (depression = 17%; anxiety = 19%) or worsened (depression = 3%; anxiety = 2%). Improvement in depression/anxiety conditions were associated with greater intensity of mystical experiences and higher ratings of the spiritual significance and personal meaning of the 5-MeO-DMT experience. There were no associations between depression or anxiety improvement and the intensity of acute challenging physical/psychological effects during the 5-MeO-DMT experience. Conclusions: Future prospective controlled clinical pharmacology studies should examine the safety and efficacy of 5-MeO-DMT administration for relieving depression and anxiety.