Using the hierarchical model of intrinsic and extrinsic motivation (HMIEM) and self-determination theory as theoretical frameworks, the purpose of the present study was to assess the role of motivation-related variables in the relationship between perceptions of social support and intentions to be physically active. Undergraduate students completed surveys assessing perceptions of social support, psychological needs satisfaction, self-determination, and future exercise intentions. Model fit with the data was examined and was considered acceptable, indicating that social support was positively related to the satisfaction of psychological needs, which, in turn, was related positively to self-determination and then to physical activity intentions.