There has been little research examining group cognitive-behavioral therapy (CBT) for schizophrenia, especially compared to an active control treatment. The purpose of this study was to investigate the effectiveness of group CBT for auditory hallucinations compared to an enhanced supportive therapy (ST). Sixty five participants with schizophrenia spectrum disorders and persistent hallucinations were randomly assigned to group CBT or enhanced group ST. Primary outcomes focused on beliefs about voices and global auditory hallucinations severity. Secondary outcomes included psychotic symptoms, self-esteem, social functioning, insight, depression, and hospitalization. Controlling for baseline levels, these outcomes were evaluated across post-treatment, 3 month and 12 month follow-ups. Participants who received enhanced ST were less likely to both resist voices and to rate them as less malevolent through 12-month follow-up relative to participants who received CBT. Group CBT was associated with lower general and total symptom scores on the PANSS through 12-month-followup relative to participants who received enhanced ST. Outcomes improved through 12-month follow-up in both therapy groups, with enhanced ST having more specific impact on auditory hallucinations, and CBT impacting general psychotic symptoms.