Based on the self-determination theory, this study investigated the mediating role of the satisfaction of the three psychological needs (need for competence, relatedness and autonomy) in the relation between need support from the physical education (PE) teacher and autonomous motivation to engage in PE and between the physical school environment and autonomous motivation to engage in PE. Data were collected from 2418 6th grade children. Analyses were performed using bootstrapping. The results showed that perceptions of competence and autonomy mediated the relation between need support from the PE teacher and autonomous motivation. Moreover, the perception of autonomy also mediated the relation between the physical school environment and autonomous motivation. These findings suggest that not only the PE teacher but also the physical school environment is able to promote autonomous motivation by satisfying the need for autonomy. (Contains 1 figure and 3 tables.)