This longitudinal intervention study examines the effectiveness of a 6-day intensive experiential group therapy program for survivors of mass shootings. The sample consisted of 36 participants (83.33% female; M age = 41.66, SD age = 22.52) who survived a mass shooting episode in the U.S. Self-reported mental health (i.e., PTSD, depression, and anxiety symptoms), physical health (i.e., sleep disturbance, subjective health complaints), and flourishing were assessed at baseline (T0), end of treatment (T1), 1-month follow-up (T2), 3-month follow-up (T3), and 6-month follow-up (T4). Satisfaction with the treatment was evaluated at T1.