This clinical trial assessed the effects of monitored naltrexone treatment in 19 subjects with schizophrenia spectrum and alcohol use disorders in an eight-week prospective open pilot study. Naltrexone was directly administered to subjects in oral doses of 100 mg on Mondays and Wednesdays, and 150 mg on Fridays. Subjects received reimbursement for attending the three weekly study visits. Subjects continued to receive their usual psychiatric care with no added alcohol counseling provided. Alcohol use was assessed by self-report and biomarkers. Psychosis severity was measured by the Positive and Negative Syndrome Scale (PANSS). Subjects reported significant reductions in their number of drinks per week, drinks per drinking day, days of drinking to intoxication, and alcohol craving. Subjects also showed significant reductions in Addiction Severity Index (ASI) alcohol composite scores and in PANSS positive, negative and general psychopathology scores.