Empirical research investigating the association between teacher pay incentives and student test scores has grown rapidly over the past decade. To integrate the findings from these studies and help inform the debate over teacher merit pay, this meta-analysis synthesizes effect sizes across 37 primary studies, 26 of which were conducted in the United States. Among the U.S. based studies, the results suggest that the effect of teacher merit pay on student test scores is positive and statistically significant (0.043 standard deviation). This summary effect varies by program design and study context, suggesting that teacher merit pay has the potential to improve student test scores in some contexts but researchers and policymakers should pay close attention to program design and implementation.