Who guides a psilocybin therapy session can significantly shape the experience for patients receiving psychedelic treatment. Across 298 participants and 670 psilocybin sessions with 60 facilitators, facilitator differences explained 13.6% of experience variation in clinical patients but only 0.8% in healthy volunteers. The effect size is larger than the typical ~8% therapist effect in conventional psychotherapy, showing that facilitator training and support can meaningfully influence psychedelic therapy outcomes.