The contribution that generalized locus of control and perceived locus of causality made to adolescents' intentions to participate in leisure-time physical activity was examined. A mediational model included constructs from three theoretical approaches: locus of control, self-determination theory (SDT), and the theory of planned behavior. A structural equation model revealed that the effects of generalized locus of control on attitudes, subjective norms, and intentions to participate in physical activity were mediated by intrinsic motives from SDT. Findings provide evidence in support of a motivational sequence in which locus of control influences situation-specific attitudes, subjective norms, and intentions mediated by the context-specific motives from SDT.