BACKGROUND Combining strategies and techniques from different therapeutic approaches is a common procedure in routine mental health practice. It has been claimed that the integration of systemic brief therapies offers useful psychotherapeutic alternatives, especially in our overloaded public mental health services. However, this claim has rarely been put to the test, and comparison with well-established empirically-based treatments has been scarce. METHODS Of 419 patients referred to an Adult Ambulatory Mental Health Service, 212 were allocated to Cognitive-Behavioral Therapy (CBT), and 207 to an integrative Brief Systemic Therapy (BST). Follow-up assessments of patients’ status took place between one and three years later. RESULTS Both therapy models were found to be equivalent in their percentage of therapeutic discharges, drop-outs, relapses and in the use of other mental health services during the follow-up period. Although both treatments were cost-efficient, BST was not briefer than CBT. The between-group equivalence was also confirmed, analyzing the data by psychiatric diagnosis. CONCLUSIONS This study provides some preliminary data that suggest that BST might be an effective and efficient treatment in public mental health practice, comparable to well-established treatments like CBT.