This study examined the direct and mediated contributions of psychosocial variables to posttreatment physical functioning among 142 patients receiving cardiac rehabilitation. Two models were proposed and tested. In the first model, psychosocial factors were correlated and made to predict baseline and 6-week physical functioning. The results showed that after controlling for age, illness severity, baseline physical functioning, and other psychosocial correlates, optimism and social support still significantly predicted better posttreatment physical functioning. In the second model, we explored both the direct and mediational relationships between psychosocial factors and physical health outcomes. Optimism and social support were found to contribute to health outcomes not only directly but also indirectly through the mediation of less engagement in detrimental coping and lower depressive symptoms, whereas hostility and negative coping only predicted outcomes indirectly through mediators. These findings highlighted the importance of addressing psychosocial issues and their interrelationships in cardiac rehabilitation.