This article reports findings from a one-year evaluation of a kindergarten math enrichment program. A randomized design was used to assess the impact of High 5s on children's math skills, attitudes towards math, language ability, and executive function for a sample of kindergarten students in New York City. High 5s math clubs were designed to provide small group math enrichment delivered in a game-like format. Participants included 655 kindergarten students in 24 schools. Students assigned to the High 5s group met outside of class in small groups with a trained facilitator three times per week. The High 5s program produced a positive impact on one of two measures of math skills. We find no impact of the program on other outcomes.