Cognitive behavior therapy (CBT) has been demonstrated in a number of randomized controlled trials to be efficacious as an adjunctive treatment for psychotic disorders. Emerging evidence suggests the usefulness of CBT interventions that incorporate acceptance/mindfulness-based approaches for this population. The current study extended previous research by Bach and Hayes (2002. The use of Acceptance and Commitment Therapy to prevent the rehospitalization of psychotic patients: A randomized controlled trial. Journal of Consulting and Clinical Psychology, 70, 1129-1139) using Acceptance and Commitment Therapy (ACT) in the treatment of psychosis. Psychiatric inpatients with psychotic symptoms were randomly assigned to enhanced treatment as usual (ETAU) or ETAU plus individual sessions of ACT. At discharge from the hospital, results suggested short-term advantages in the ACT group in affective symptoms, overall improvement, social impairment, and distress associated with hallucinations. In addition, more participants in the ACT condition reached clinically significant symptom improvement at discharge. Although 4-month rehospitalization rates were lower in the ACT group, these differences did not reach statistical significance. Decreases in the believability of hallucinations during treatment were observed only in the ACT condition, and change in believability was strongly associated with change in distress after controlling for change in the frequency of hallucinations. Results are interpreted as largely consistent with the findings of Bach and Hayes and warrant further investigations with larger samples.