This study aimed at determining the effectiveness of group cognitive behavior therapy (CBT) for recent onset psychosis in comparison with a recognized intervention for individuals with severe mental illness-social skills training. One hundred twenty-nine participants took part in a single-blind randomized controlled trial with repeated measures (baseline, 3 months, and 9 months). Participants were randomized to 1 of 3 conditions: group CBT, group social skills training for symptom management, or a wait-list control group. Both interventions were delivered by mental health staff with minimal training. Both treatments resulted in improvements on positive and negative symptoms compared with the wait-list control group, with the CBT group having significant effects over time on overall symptoms, and post-treatment effects on self-esteem, and active coping skills compared with the wait-list control group and lower drop-out rates than the skills training group. Therapist fidelity was adequate for both treatment conditions. Group CBT for psychosis is a promising intervention for individuals with recent onset of psychosis and their mental health professionals.