<p>Psychological needs satisfaction and autonomous motivation are crucial for children’s academic success, especially in the context of a school transition. While parents can support these motivational resources by providing an autonomy-supportive environment, the ability to establish such an environment is not innate and can be acquired through learning. Targeting mothers, the goal of the present experimental study was to evaluate the effects of an online education program for parents whose child was transitioning to secondary school. The sample included 148 mother-child dyads who completed questionnaires prior (in Grade 5) and after the transition (in Secondary 2). Results indicated that compared to mothers assigned to the control condition, those in the intervention group reported providing more autonomy support at 18 months post-test. Moreover, children of mothers in the intervention group reported experiencing less maternal control, stronger competence satisfaction, and lower levels of amotivation compared to children of mothers in the control group. These findings are discussed in the context of self-determination theory and parent training programs.</p>