The purpose of this study was (a) to examine gender and age differences in college students' perceived competence, enjoyment, persistence, and leisure time moderate-to-vigorous physical activity (MVPA), and (b) to utilize a structural equation modeling (SEM) to assess the direct and indirect effects of enjoyment and perceived competence on MVPA through the mediator of persistence. A total of 440 college students participated in this study. Multivariate analysis of variance and univariate analysis of variance revealed that male students scored significantly higher on enjoyment, perceived competence, and MVPA. The SEM showed that both enjoyment and perceived competence had a significant direct impact on students' MVPA. However, persistence did not mediate the path between MVPA and the two exogenous variables (enjoyment and perceived competence). The findings not only advance understanding of the motivational determinants on college students' MVPA, but also highlight the role gender plays in enhancing college students' participation in MVPA.