Background: School belonging has been linked to students' health and well-being. As US schools become more ethnically diverse, it is important to understand how schools can contribute to a sense of belonging for students from all ethnic groups. Methods: The present study examines the association between school interethnic climate, school belonging, and 3 well-being indicators (psychological, physical, and academic) among 657 10th graders across 2 states. Results: Positive school interethnic climate was associated with stronger feelings of school belonging, and was indirectly associated with better psychological adjustment, fewer physical symptoms, and better grades via school belonging. There were no differences between White and non-White students in the findings. Conclusions: Focusing on fostering a positive interethnic atmosphere may be a useful target for schools to support students' health and well-being as well as academic performance.