Background: Autistic children can benefit from physical activity (PA) in a variety of ways. However, autistic children tend not to meet PA recommendations and, consequently, may not experience the associated benefits. Parental PA support can facilitate PA participation among autistic children, but parents of autistic children may lack the skills to help their child engage in PA. Few studies, to date, have examined the outcomes of parent-mediated PA interventions for autistic children. The purpose of this study was to explore parents’ perceived behavioral control (PBC) to support their autistic children in PA after their participation in a PA intervention. Methods: The theory of planned behavior served as the framework for this descriptive–qualitative investigation. Fifteen parents (each with 1 autistic child in the intervention) participated in semistructured interviews (3 wk after the intervention), which were transcribed and then analyzed using thematic line-by-line analysis. Results: Three themes characterized the changes to parents’ PBC after completing the PA intervention. Those themes were: (1) I learned by son! (2) You are my coach! and (3) I can do it! Conclusions: The results showed that by participating in a parent-mediated PA intervention, parents experienced improved confidence and awareness of their child’s abilities, thus enhancing their PBC. Future research is needed to examine how these improvements in PBC may influence the actual PA behaviors of autistic children.