As maintenance of lifestyle change and risk factor modification following completion of cardiac rehabilitation has been shown to be notoriously difficult, we developed a brief self-regulation lifestyle program for post-cardiac rehabilitation patients. Randomized-controlled trial. Following completion of cardiac rehabilitation 210 patients were randomized to receive either a lifestyle maintenance program (n = 112) or standard care (n = 98). The program was based on self-regulation principles and consisted of a motivational interview, 7 group sessions and home assignments. Risk factors and health behaviors were assessed at baseline (end of cardiac rehabilitation), and 6 and 15 months thereafter. ANCOVAs showed a significant effect of the lifestyle program on exercise behavior at 15-month follow-up. Mediation analysis demonstrated that the treatment effect on exercise behavior could be explained by self-regulation skills. Chi squared tests showed that patients in the intervention group had significantly fewer uncontrolled risk factors as compared to the control group. Finally, the lifestyle intervention program was associated with a 12 % reduction in self-reported cardiac hospital admission rates. This trial indicates that a relatively brief, theory-based lifestyle program is capable of inciting and maintaining improvements in exercise adherence. It is suggested that patients may need ongoing attention and guidance, for example in the form of (internet-based) booster sessions, as long-term consolidation of changes is arduous.