<p>This study aimed to comprehensively understand how children engaged with physical activity in after-school programs developed through a university-community partnership initiative. The program was designed to enhance physical activity opportunities for elementary school students by offering a variety of structured and unstructured activities, facilitated by physical education teacher education (PETE) major students serving as mentors. A mixed-methods approach was employed, using both quantitative and qualitative data. Seventy children completed the Physical Activity Enjoyment Scale (PACES) before and after participating in a 12-week program. Additionally, 68 children participated in focus group interviews, and 32 physical education major students provided written reflections. Data were collected during the spring semester of 2025 from four elementary schools. Quantitative findings indicated an increase in children’s enjoyment of physical activity from pre- to post-test. Qualitative analysis revealed four central themes: (a) enjoyment of the after-school program, (b) engagement in physical activity, (c) learning through play, and (d) positive relationships with mentors. This study demonstrates that prioritizing enjoyment, autonomy, social connection, and authentic learning within playful physical activity in after-school programs is paramount for fostering children’s long-term engagement. The university-community partnerships create a synergistic “win-win” environment, where the involvement of PETE major students as mentors not only enriched children’s experiences but also provided valuable teaching practice for university students. Such partnerships are essential for building high-quality after-school programs that equip children with lifelong healthy habits and foster their overall well-being.</p>