Purpose: Using self-determination theory, this study examined unique contributions of relatedness need satisfaction (to both teachers and peers) to intrinsic motivation and engagement (behavioral, cognitive, and emotional) over and above those of autonomy need satisfaction and competence need satisfaction among Turkish students in secondary school physical education. Method: Participants were 331 (162 boys, 169 girls) middle and high school students enrolled in physical education classes at four public schools in the southwest Turkey. Data were collected by previously validated questionnaires. Results: No gender differences occurred in the mean levels of relatedness to teachers need satisfaction and relatedness to peers need satisfaction. These two types of relatedness need satisfaction made significant unique contributions to student engagement for both boys and girls. The differential roles of relatedness to peers need satisfaction in predicting boys' and girls' engagement were observed. Discussion/Conclusion: The study demonstrated that two types of relatedness need satisfaction uniquely predicted students' engagement in a secondary school physical education setting. This finding supports self-determination theory that relatedness need satisfaction is an important motivator for students in schools.