Background The literature suggests that cognitive reactivity in bipolar patients can increase relapse vulnerability, is enhanced by depressive mood and dysfunctional attitudes, and could be improved with MBCT. Autobiographical memory (AM) could be involved in cognitive reactivity, and improved with MBCT training. This study aims to investigate the effect of MBCT for bipolar patients on depressive and anxious symptoms, dysfunctional attitudes and AM, and the predictive versus mediating role of AM in the impact of MBCT on clinical symptoms. Methods Sixty-two outpatients diagnosed with bipolar I disorder were assigned to MBCT and were compared to 37 bipolar patients on a waiting list. Affective symptoms and dysfunctional attitudes were explored using self-report inventories (BDI, BAI, DAS) and AM was assessed using the Autobiographical Memory Test. Results Patients receiving MBCT demonstrated significantly decreased depressive symptoms, dysfunctional attitudes, overgeneral memories and omissions, and increased specific memories. General AM and omissions at baseline respectively predicted lower anxiety and dysfunctional attitudes improvement following therapy, but the improvement of AM did not explain the impact of MBCT on depression and dysfunctional attitudes improvement. Limits Further studies should consider patients’ therapeutic adherence and mechanisms involved in MBCT in order to better apprehend how MBCT may reduce dysfunctional attitudes and improve AM in bipolar patients. Conclusion Results are consistent with the hypothesis that MBCT reduces cognitive reactivity and AM impairment in bipolar disorders. Findings suggest that AM training prior to MBCT may influence MBCT efficacy, but that MBCT efficacy on AM and clinical symptoms are non-related phenomena.< Réduire