Objective: With high rates of mental health concerns on college campuses, effective positive psychology interventions could greatly improve student well-being and academic outcomes. Participants: Working undergraduates (N = 52). Methods: This preliminary, randomized controlled trial investigated the effects of the 8-week Mindfulness-based strengths practice (MBSP) on Seligman's five domains of well-being, as measured by the PERMA-Profiler, Workplace PERMA-Profiler, and student retention in working undergraduates. Results: Students in the MBSP intervention had significantly higher well-being, engagement, meaning, and health following the MBSP program (P < 0.0042). No such changes were observed in the control group. Students in the intervention group also had modestly higher retention rates in the following academic year than those in the control group. Conclusions: This study provides the first evidence to date that an MBSP program can improve college student well-being and retention.