The authors investigated relationships among family support for healthy nutrition, fruit and vegetable intake, and social-cognitive mediators such as intention, self-efficacy, and planning. Participants were 130 myocardial infarction survivors (64% men) treated in 4 clinics in Poland. The authors collected self-reported data across 8 months during and after cardiac rehabilitation (at the beginning of rehabilitation, 2 weeks after rehabilitation, and 6 months later). Results indicate that directly after rehabilitation, less than 20% of patients met recommended guidelines for fruit and vegetable intake, with a further decrease in fruit and vegetable consumption over time (14% and 12% at follow-ups). Family support predicted patients' behavior at follow-up, with self-efficacy playing a mediating role. Although regular formation of action plans predicted fruit and vegetable intake, it did not mediate social support-behavior relationships.