To address gaps in the youth participation and adolescent physical activity (PA) promotion literature, we examined the feasibility of youth participatory action research (YPAR) in (a) general aftercare (YPAR only) and (b) with a physical activity intervention, (YPAR + PA) to reach marginalized youth and impact individual empowerment and second-order change for equitable PA access. We intervened during middle school, a developmental stage conducive to changing health habits. We used a concurrent, mixed-method triangulation design. Participants were students (94% non-Hispanic Black/African American, 75% free/reduced lunch) in the southeastern United States. YPAR was adapted from online modules. Youth conducted photovoice, capturing and analyzing social/environmental factors contributing to inequities in their schools/programs. PA inequities emerged for girls. Findings indicated feasibility of YPAR with systems supports. Changes occurred at the individual and systems level in the YPAR + PA program. Sociopolitical skills, participatory behavior, and perceived control empowerment subdomains increased pre-post, and youth qualitative responses aligned. A follow-up interview with the director revealed all youth-proposed changes occurred. A feedback loop was developed for continued youth input. Youth-led changes to increase PA access have potential to decrease health disparities by generating unique solutions likely missed when adults intervene alone. Highlights Gaps in the youth participation and physical activity intervention literature are addressed. YPAR was implemented in aftercare, and with a physical activity intervention for youth-led change. Individual/systems change occurred in the program with YPAR with a physical activity intervention. Strategies for decreasing physical activity disparities are discussed.