Light-touch social psychological interventions have gained considerable attention for their potential to improve academic outcomes for underrepresented and/or disadvantaged students in postsecondary education. While findings from previous interventions have demonstrated positive effects for racial and ethnic minority and first-generation students in small samples, few interventions have been implemented at a larger scale with more heterogeneous student populations. To address this research gap, 7,686 students, representing more than 90% of incoming first-year students at a large Midwestern public university, were randomly assigned to an online growth mindset intervention, social belonging intervention, or a comparison group. Results suggest that after the fall semester, the growth mindset intervention significantly improved grade point averages for Latino/a students by about 0.40 points. This represents a 72% reduction in the GPA gap between White and Latino/a students. Further, this effect was replicated for both spring semester GPA and cumulative GPA. These findings indicate that light-touch interventions may be a minimally invasive approach to improving academic outcomes for underrepresented students. Our findings also highlight the complexity of implementing customized belonging interventions in heterogeneous contexts.