Objectives We investigated the feasibility and acceptability of an integrated group therapy (called HABIT) for comorbid bipolar disorder (BD) and alcohol and substance use disorders (ASUD) (BD-ASUD), a disabling clinical presentation for which no specific treatment has been validated. The 14-session HABIT programme employs psychoeducation-oriented cognitive-behaviour therapy (CBT) followed by mindfulness-based relapse prevention (MBRP) therapy. Method Potential group participants were recruited from adult clients with a DSM-IV diagnosis of BD and an ASUD who were referred by their treating clinician. Observer-rated changes in mood symptoms and ASUD, attendance rates and subjective feedback are reported. Results Eight of 12 clients referred to the programme initially agreed to join the group, six attended the first group session and five clients completed the programme. Group mean scores for mood symptoms improved over time, with slightly greater reductions in depression during the first module. About 50% of individuals showed clinically significant improvement (≥30% reduction) in alcohol and substance use. Attendance rates showed some variability between individuals and across sessions, but the average attendance rate of the group was marginally higher for the first module (86%) as compared with the second module (77%). Most clients reported high levels of general satisfaction with a group specifically targeted at individuals with BD-ASUD. Conclusion This small pilot study suggests our intensive group therapy is acceptable and feasible. If findings are replicated, we may have identified a therapy that, for the first time, leads to improvement in both mood and substance use outcomes in clients with difficult-to-treat comorbid BD-ASUD. Copyright © 2016 John Wiley & Sons, Ltd. Key Practitioner Message Comorbidity between bipolar and alcohol and substance use disorders (BD-ASUD) is frequent and highly disabling;, Therapeutic research on approaches that can simultaneously help BD and ASUD is lacking;, Previous research highlights the need for integrated treatment of both conditions but showed improvements limited to either element of the comorbid disorder;, This pilot study supports the feasibility and acceptability of an intensive, 14-session group therapy programme that integrates CBT and mindfulness approaches. [ABSTRACT FROM AUTHOR]