Research on mindfulness-based cognitive therapy (MBCT; Segal, Williams, & Teasdale, 2002a) has supported the effectiveness of this approach for use with preventing relapse in recurrent depression. This study evaluated the use of MBCT in a heterogeneous sample of 26 psychiatric outpatients with mood and/or anxiety disorders. Results from both completer and intent to treat analyses showed that MBCT was associated with statistically significant improvements in depression, anxiety, stress, and insomnia symptoms. Rates of clinically significant improvement were comparable with effectiveness studies of cognitive behaviour therapy and mindfulness-based stress reduction in heterogeneous samples. It is concluded that MBCT may be of value for a range of psychological presentations, administered in heterogeneous groups. Future, controlled, research is required to further evaluate this conclusion and to investigate mechanisms of change.