Objective: This study aimed to assess the age-varying prevalence of and association between school belonging and flourishing among sexual or gender minority (SGM) and racial or ethnic minority (REM) students compared with non-minority students in the U.S. college setting. Participants: Data were drawn from a 2017-2018 national survey of U.S. college and university students ages 18-26. Method: Data were examined using varying-coefficients models to estimate the relation of school belonging and flourishing across ages 18-26. Results: SGM students ( = 6,718) and REM students ( = 10,539) reported significantly lower belonging and flourishing than cisgender heterosexual students ( = 19,492) and white students ( = 16,444), respectively, at several age points. The association of belonging with flourishing was significantly greater for SGM students than for cisgender heterosexual students across all ages. Conclusions: Findings of this study underline the important role of school belonging in socioemotional flourishing for SGM young adults.