Sport involvement may offer physical and psychological benefits to early adolescents beyond those accrued through physical activity (PA). Those benefits, though, may be moderated by gender. The purpose of this study was to examine these potential benefits in a middle school population. The sample consisted of 629 sixth graders enrolled in a physical education (PE) course. Students completed self-report measures on sport involvement, PA self-efficacy, and physical self-concept. During PE, students completed FitnessGram testing, which provided measurements of cardiorespiratory fitness (CRF), muscular strength and flexibility, and body composition. MANCOVA analyses were used to examine the interaction between sport involvement and gender in relation to the psychological and physical outcomes. Multivariate analyses demonstrated no Sport x Gender interactions for any outcome; sport involvement, however, was related significantly to improvements in CRF, muscular strength, PA self-efficacy, and physical self-concept (aerobic endurance and muscular strength). The findings suggest that sport involvement, above what may be attained through standardized, school-based PE experiences, uniquely provides physical and psychological benefits for early adolescents.