This article examines the impact of proactive, data-informed success coaching on students' retention and completion outcomes, drawing on theories of student engagement and a five-year (2016-2020), mixed-methods study of coaching conducted across 10 North Carolina community colleges. Results from a randomized controlled trial show that coaching increased students' longer-term retention, with especially notable effects among Black students and among men. A paired implementation study suggests that effects of coaching are greater when students have the opportunity to engage with the same coach over time, and when colleges implement coaching with fidelity and with strong institutional leadership, communication, and support.