The purpose of this study was to examine the effects of integrating mathematics into physical education. Participants included 132 fourth grade students from four physical education classes at two schools. In-tact physical education classes were assigned to intervention and control groups. Mathematics activities were integrated into the intervention group's physical education classes for seven weeks. Data collection included three assessments of mathematics performance: mathematics grades, standardized mathematics assessment scores, and mathematics unit assessment scores. Data were collected pre- and post-intervention from the intervention and control groups, and data were analyzed using mixed nested ANOVA. Results showed that across all measures of mathematics performance students in both groups significantly improved from pre- to post-intervention. Significant differences based on the interaction of time (pre-/post-test) and group (intervention/control) were evident in mathematics unit assessment scores. These findings add to the growing body of literature of integrated curriculum in physical education.