Importance Childhood vaccination rates have declined in many US states, contributing to outbreaks of vaccine-preventable diseases and raising concerns about policy effectiveness amid growing vaccine hesitancy. Objective To evaluate the association between state repeal of nonmedical vaccine exemptions and kindergarten vaccination rates. Design, Setting, and Participants This cross-sectional study used annual state-level kindergarten vaccination and exemption data from the Centers for Disease Control and Prevention for school years 2011 through 2023. A staggered difference-in-differences design compared states that repealed nonmedical exemptions with states that maintained such policies. The study included kindergarten students in US public and private schools across 37 to 43 states, depending on the outcome measure. Exposures Total repeal of nonmedical vaccine exemptions in California (2015), New York (2019), Maine (2019), and Connecticut (2021). Partial repeal in Vermont (2015) and Washington (2019) was analyzed separately. Main Outcomes and Measures State-level kindergarten vaccination rates for diphtheria-tetanus-acellular pertussis (DTaP), hepatitis B, measles-mumps-rubella (MMR), and poliovirus (polio) vaccines; rates of medical and nonmedical exemptions. Results Among 4 states with total repeal affecting approximately 2.8 million kindergarten students, repeal of nonmedical exemptions reduced overall exemption rates by 3.2 (95% CI, 1.9-4.4) percentage points within 3 years. Compared with nonrepeal states, vaccination rates rose by 4.1 (95% CI, 3.3-4.9) percentage points for DTaP, 2.8 (95% CI, 2.1-3.5) percentage points for hepatitis B, 4.0 (95% CI, 3.1-4.9) percentage points for MMR, and 3.8 (95% CI, 2.9-4.6) percentage points for polio. Minimal substitution toward medical exemptions occurred, an increase of only 0.4 (95% CI, 0.04-0.7) percentage points. Partial repeal of nonmedical exemptions demonstrated smaller, less persistent increases in vaccination rates. Conclusions and Relevance State repeal of nonmedical vaccine exemptions was associated with increased kindergarten vaccination rates with minimal substitution toward medical exemptions. These findings suggest that nonmedical exemption repeal played a role in maintaining vaccination coverage in repeal states during a period of heightened vaccine hesitancy.