Athletic identity (AI) is associated with increased motivation across a broad age range of exercisers. The study of AI and Masters athletes (MAs) has received less attention. The relationship between AI and motivation was tested with a large sample of MAs (n = 455; Mage = 51.97, SD = 11.51). MAs completed the Athletic Identity Questionnaire (AIQ) and Behavioral Regulation in Sport Questionnaire (BRSQ). Confirmatory factor analyses supported the four-factor (i.e., appearance, importance, competence, encouragement) structure of the AIQ (X2(183) = 384.02, p < .005, CFI = .944, RMSEA = .049) and the six-factor (i.e., intrinsic, integrated, identified, introjected, external and amotivation) structure of the BRSQ (X2(237) = 646.26, p < .005, CFI = .872, RMSEA = .062). The structural model (X2(900) = 1682.28, p < .005, CFI = .901, RMSEA = .044) showed significant relationships between the importance of sport and MAs' intrinsic (B = .167), integrated (B = .227), identified (B = .249), and external (B = -.239) motives. MAs' competence was related to intrinsic (B = .171), identified (B = .173), introjected (B = -.312) motives, and amotivation (B = -.229). MAs' perceived encouragement was related to integrated (B = .127), identified (B = .169), and introjected (B = .124) motives, and amotivation (B = -.137). Generally, when MAs identify strongly with their athletic role, they are also likely to have high levels of self-determined and low levels of non-self-determined motives for sport. The results are encouraging considering the established link between self-determined motives and sport commitment.