Organized sport is a context in which to promote positive youth development (PYD). Interventions with a PYD lens are often implemented to promote a wide range of physical or psychosocial benefits through sport participation. To date, no meta-analytic review of the effect of these interventions has been conducted. This is important because such interventions are held in high regard when it comes to policy development. In the present study, we conducted seven meta-analyses to evaluate the overall effect of sport-based interventions on PYD outcomes. Aspects of the study design and sample also were tested as moderators. In total, 35 studies (from 29 published articles) reporting on 74 effect sizes highlighted small to medium effects of PYD interventions on competence, confidence, and life skills outcomes. No significant overall effects were found for outcomes related to character, connection, PYD climate, and health. Further, moderation analyses showed that: (a) character was moderated by study design, sport type, and study duration; (b) competence was moderated by design and participant sex; and, (c) life skills were moderated by design, sport type, duration, and participant age. Implications for theory and practice concerning the use of sport-based interventions to influence PYD are discussed.