Colleges and universities are paying increasing attention to students' transition into post-secondary education, including the provision of support to freshmen through structured First-Year Experiences (FYEs). Although low- and-moderate-income students are participating in post-secondary education at increased rates, their performance remains behind that of affluent students. We evaluated the effects of a two-arm experimental-assignment treatment for low- and moderate-income U.S. students eligible for Federal Pell grants at a four-year high-research university (N = 178): 57 control condition, 61 in professional learning communities, 60 in community mentoring, with computerized random assignment conducted by an external evaluator. The intensive (3 credit) two-semester research-based FYE plus mentoring program showed no effect on students' GPA or likelihood of good academic status, probation, or year two persistence. The treated students also showed no differences in fall-to-spring growth or spring level for non-cognitive measures, including academic engagement, amotivation, peer interaction, faculty interaction, and staff interaction. The null findings are consistent across unadjusted treatment-control comparisons, multivariate regression analyses for continuous outcomes, and logistic, probit, or linear analyses of dichotomous outcomes. Our findings have implications for generalizability about FYE effectiveness for low- and moderate-income students and for the design characteristics of FYE programing to reliably improve student outcomes.