OBJECTIVE: To explore the short- and long-term mental health resource utilization and cost of care in a sample of 120 individuals with bipolar disorders who participated in a randomized controlled efficacy trial of group psychoeducation versus unstructured group support. METHOD: Prospective, independent monitoring of DSM-IV bipolar disorder type I or II patients aged 18 to 65 years was conducted during the intervention phase (6 months) and follow-up phase (5-year postintervention) of a randomized controlled trial reporting clinical outcomes and inpatient and outpatient mental health service utilization, with estimation of cost of treatment per patient. The study was conducted from October 1997 through October 2006. RESULTS: Compared with individuals with bipolar disorder receiving the control intervention, psychoeducated patients had twice as many planned outpatient appointments, but the estimated mean cost of emergency consultation utilization was significantly less. There were trends for psychoeducated patients to opt for self-funded psychotherapy after completing group psychoeducation and to utilize more medications. However, inpatient care accounted for 40% estimated total cost in the control group but only about 15% in the psychoeducation group. CONCLUSIONS: This study demonstrates the importance of taking a long-term overview of the cost versus benefits of adjunctive psychological therapy in bipolar disorders. If viewed only in the short-term, the psychoeducation group used more mental health care resources without clear additional health gain. However, extended follow-up demonstrated a long-term advantage for psychoeducated individuals, such that, compared to an unstructured support group intervention, group psychoeducation is less costly and more effective.