ObjectivesTo examine outcome after mindfulness training in a heterogeneous psychiatric outpatient population and to compare outcome in different diagnostic groups. Method One hundred and forty‐three patients in 5 diagnostic categories completed questionnaires about psychological symptoms, quality of life, and mindfulness skills prior to and immediately after treatment. Results The mixed patient group as a whole improved significantly on all outcome measures. Differential improvement was found for different diagnostic categories with respect to psychological symptoms and quality of life: Bipolar patients did not improve significantly on these measures. This finding could be explained by longer illness duration and lower baseline severity in the bipolar category. Conclusion Mindfulness training is associated with overall improvement in a heterogeneous outpatient population. Differences in outcome between diagnostic categories may be ascribed to differences in illness duration and baseline severity.