Self-identity influences physical activity participation, and individuals who are motivated by self-determined and volitional reasons are more likely to maintain their exercise behavior. The present study incorporates tenets of identity theory and self-determination theory to investigate the relationships among identity, motivation, and physical activity in former college athletes. Former Division I student-athletes (N = 282) completed an online survey consisting of the Exercise Identity Scale, the Athletic Identity Measurement Scale, the Behavioral Regulation for Exercise Questionnaire, the Godin Leisure Time Exercise Questionnaire, and demographic items. Exercise identity and athletic identity were both positively related to physical activity and significantly interacted in their prediction of physical activity participation. Motivation, and specifically identified regulation, appears to have a mediating effect on the relationship between exercise identity and physical activity. The findings of this study add to our understanding of former college athletes’ physical activity behavior within an identity and self-determination theory framework.