Purpose: This study examines the impact of participation in a STEM Enrichment Summer Bridge Program, funded by the NSF Houston-Louis Stokes Alliance for Minority Participation, on undergraduate student success outcomes, particularly for under-represented students. Design/methodology/approach: The study uses propensity score matching and logistic regression analysis to examine the effects of participation in the STEM enrichment program on graduation and retention in STEM after matching on baseline socio-demographic and pre-college characteristics. Findings: The analysis found that program participation had a significant effect on increasing both the graduation rates and retention of under-represented minority students in STEM fields. In addition, results indicated that program participation had a particularly strong impact for Pell-eligible students in terms of course grades. Research limitations/implications: Data obtained for this study were limited to a single Hispanic-serving/Asian-serving institution, and therefore are not necessarily representative of the graduation and retention trends of the larger population of underrepresented minority (URM) students across the nation. Originality/value: This study uniquely adds to the existing body of literature surrounding the retention of URM students in STEM fields by accounting for baseline variables, such as pre-college academic achievement and socio-demographic characteristics, that could lead to bias in estimating results. Specifically, this study addresses limitations of previous studies by comparing participants and non-participants of the STEM enrichment program who are matched on a selection of baseline characteristics.