Objective: To provide evidence of the effectiveness of a brief relapse prevention intervention using implementation intentions (Self-Management after Therapy, SMArT), following remission from depression and to identify effective relapse prevention strategies. Method: The SMArT intervention was provided to 107 patients who were recovered after psychological therapy for depression. Relapse events were calculated as reliable and clinically significant increases in PHQ-scores. Sixteen patients receiving the intervention and eight practitioners providing it were interviewed. Framework Analysis identified seven themes which highlighted effective relapse prevention strategies and effective implementation of the SMArT intervention. Results: Relapse rates at the final SMArT session (four months after the end of acute stage therapy) were 11%. Seven themes were identified that supported effective self-management: (1) Relationship with the practitioner—feeling supported; (2) Support networks; (3) Setting goals, implementing plans and routine; (4) Changing views of recovery; (5) The SMArT sessions—mode, content, timing, duration; (6) Suitability for the person; and (7) Suitability for the service. Conclusion: The study provides some support for the effectiveness of the SMArT intervention, although a randomized controlled trial is required; and identifies important relapse prevention strategies.