Objective: Sport is an important source of physical, social and emotional health and well-being among children. Sports participation at school may provide young people with the opportunity to build interpersonal skills and develop supportive social relationships with peers and adults, which may translate to positive experiences during the school day. School climate represents the relationships, values and beliefs within a school system and is associated with positive social, emotional and psychological health outcomes. This research examines the influence of social relationships developed during an after-school sports programme on indicators of school climate. Method: Students in grades 4-8 (n = 230) at a school in Phoenix (Arizona) completed an online survey to measure perceptions of peer and coach relationships in after-school sports and indicators of school climate in the form of engagement with students, teachers and the school itself and perceptions of the school environment. Associations between sports relationships and school engagement and environment were examined through structural equation modelling (SEM). Results: Feeling coaches care about players and feeling like part of a team were positively associated with reported levels of school engagement. Feeling like other students shared similar values during sports, feeling a sense of belonging and feeling that coaches cared were associated with positive perceptions of school environment. Conclusion: Participation in an after-school sports programme can provide an opportunity for young people to develop positive social relationships with peers and coaches which may contribute to positive perceptions of the learning environment and student engagement during the school day. Findings support efforts to increase opportunities and accessibility to sports during the school day.