The evidence base for treatment of bipolar affective disorder (BD) demands the evaluation of new psychotherapies in order to broaden patient choice. This study reports on the feasibility, safety, helpfulness and effectiveness of cognitive analytic therapy (CAT). In a pilot randomized controlled trial, BD patients in remission were randomized to either receiving 24 sessions of CAT (n = 9) or treatment as usual (n = 9) and were assessed in terms of symptoms, functioning and service usage over time. In the CAT arm no adverse events occurred, 8/9 completed treatment, 5/8 attended all 24 sessions and 2/8 were categorized as recovered. The most common helpful event during CAT was recognition of patterns in mood variability, with helpfulness themes changing according to phase of therapy. No major differences were found when comparing the arms over time in terms of service usage or psychometric outcomes. The study suggests that conducting further research into the effectiveness of CAT in treating BD is warranted and guidance regarding future trials is provided. Copyright © 2016 John Wiley & Sons, Ltd. Key Practitioner Message Treating BD with CAT appears feasible and safe. Retaining fidelity to the reformulation, recognition and revision structure of CAT appears useful. Participants stated that across the phases of CAT, focussing on patterns of mood variability was consistently helpful.