The provision of grant aid is important to students' postsecondary opportunities and success. It is well established that grant aid increases the probability of enrollment in postsecondary education. A slate of studies in recent years has extended this research to examine whether grant aid also has an impact on persistence and degree attainment. This article presents a systematic review and meta-analysis of the best available evidence of the effect of grant aid on postsecondary persistence and degree attainment. The systematic review identifies and describes the landscape of the literature on grant aid programs and their effects on postsecondary success. A meta-analysis of 43 studies yielding 75 effect sizes estimates that grant aid increases the probability of student persistence and degree completion between 2 and 3 percentage points. When considering the dollar amount of aid, we estimate an additional $1,000 of grant aid improves persistence and attainment by 1.5 to 2 percentage points. Suggestions for future research and implications for policy are discussed.