Objective: To assess psychometric properties of the Commitment to Physical Activity Scale (CPAS). Methods: Girls in third to fifth grades (n = 932) completed the CPAS before and after a physical activity intervention. Psychometric measures included internal consistency, factor analysis, and concurrent validity. Results: Three CPAS factors emerged: values, attitudes, and motivation, with reliability coefficients ranging from 0.429 to 0.821. Significant correlations existed between subscales and physical activity frequency. Conclusions: The CPAS was reliable and valid and in a sample of third-to fifth-grade girls. Findings support using the CPAS for measuring overall commitment to physical activity in girls.