The authors examine the effects of a comprehensive college transition program (CCTP) on four psychosocial outcomes associated with postsecondary success: sense of belonging, mattering, and academic and social self-efficacy. The CCTP operates on three four-year campuses and includes a range of supports, including shared academic courses, peer mentoring, and residential or common community spaces. They leverage the randomization of Angrist et al. (2014), but restrict their comparison to scholarship recipients with and without CCTP exposure. To account for differential attrition from the experimental sample, they rely on a “selection on observables” assumption for their primary analysis. Results suggest that the program significantly and substantially increased students’ sense of belonging and mattering, but had no effect on academic or social self-efficacy.