After‐school programmes (ASPs) often provide youth with a safer alternative to unstructured time while providing a context for building skills and forging positive relationships with programme staff and peers. ASPs may be particularly effective for youth with marginalized identities, including youth of colour and youth from low‐income backgrounds. Despite this promise, few rigorous evaluations of ASPs have been conducted and even fewer meta‐analyses have investigated the effects of ASPs among youth with marginalized identities. Using a multi‐level meta‐analysis of 615 effect sizes across 56 studies (overall n = 128,538), the current study examined the overall effects of ASPs on internalizing, externalizing, school‐related, social functioning, and self‐perception/identity outcomes among kindergarten through 12th grade youth with marginalized identities. Results indicated ASPs to have a small, yet significant positive overall effect on youth outcomes (g = 0.2049, p = .001, 95% CI = 0.08–0.33). Moderator analyses revealed significant differences in effects based on outcome source and outcome measure type. Given the ubiquity of ASPs and the challenges that youth experiencing marginalization face, this study uniquely adds to the existing literature and outlines important implications and recommendations for research, policy, and practice.