The objective of this study was to estimate the extent to which motivational regulations influence physical activity behavior through role identity among people 55years or older. Participants (N = 409; Mage = 66.29years [SD = 7.06]) completed online questionnaires to measure motivational regulations, role identity, and the frequency of physical activity in a typical week and in the past month. Mediation analysis using ordinary least squares path analysis revealed that autonomous forms of motivational regulation (positively) and controlled forms of motivational regulation (negatively) influenced role identity, which then positively influenced physical activity behavior. Bootstrap confidence intervals (95%) for the indirect effects (a × b) based on 5,000 bootstrap samples were entirely above or below zero. These findings point to future experimental evaluations of interventions aiming at both increasing and decreasing autonomous and controlled motivational regulations, respectively, to promote physical activity behavior through role identity.