OBJECTIVES The aim of the present study was to test two brief planning interventions designed to encourage cardiac patients to engage in regular physical exercise following discharge from rehabilitation. The interventions comprised action plans on (a) when, where, and how to act, and (b) coping plans on how to deal with anticipated barriers. DESIGN AND METHOD An experimental longitudinal trial was conducted to test two interventions that either focused on action planning alone, or on a combination of action planning and coping planning. A total of 211 participants completed assessments at baseline and 2 months after discharge. Participants were randomly assigned to either one of the intervention groups or a standard-care control group. RESULTS Participants in the combined planning group did significantly more physical exercise 2 months post-discharge than those in the other groups. CONCLUSIONS The theoretical distinction between action planning and coping planning as introduced in the present study has proven useful in explaining changes in health-related behaviour. The combined planning intervention can be applied in the context of cardiac rehabilitation programmes.