Purpose: A primary goal of physical education is to develop physically literate individuals with the knowledge, skills, and confidence necessary for a physically active lifestyle. Guided by the expectancy-value and interest motivation theories, the purpose of this study was to identify the relationship between students' motivation and health-related fitness knowledge developed in physical education and their after-school physical activity participation. Method: Third-, 4th-, and 5th-grade students (N = 293) from 6 elementary schools in a large metropolitan school district in the United States provided data on expectancy beliefs and perceived task values, situational interest, health-related fitness knowledge, and after-school physical activity. Data were analyzed using descriptive statistics and a simultaneous multiple regression model. Results: It was found that expectancy beliefs (ß = 0.20, t = 2.16, p = 0.03) and perceived exploration demand (ß = 0.25, t = 2.58, p = 0.01), a source for situational interest, were positively related to after-school physical activity. The 2 variables, however, accounted for only 11.2% of the variances for children's after-school physical activity participation. Conclusion: This study demonstrates that students' active exploration and expectancy beliefs for success in physical education have limited influence on leisure-time physical activity participation.