The present study examined the impact of a brief version of an acceptance-based treatment (acceptance and commitment therapy; ACT) that teaches patients to accept unavoidable private events; to identify and focus on actions directed toward valued goals; and to defuse from odd cognition, just noticing thoughts rather than treating them as either true or false. Eighty inpatient participants with positive psychotic symptoms were randomly assigned to treatment as usual (TAU) or to 4 sessions of ACT plus TAU. ACT participants showed significantly higher symptom reporting and lower symptom believability and a rate of rehospitalization half that of TAU participants over a 4-month follow-up period. The same basic pattern of results was seen with all participant subgroups except delusional participants who denied symptoms.