Research on the relationship between after-school program participation and student outcomes has been mixed, and beneficial effects have been small. Most recent studies suggest that participation is best characterized as a multidimensional concept that includes enrollment, attendance, and engagement, which help explain differences in student outcomes. The present study uses data from a longitudinal study of after-school programs in elementary schools to examine staff ratings of student engagement and school outcomes. The factor structure of the staff-rated measure of student engagement was examined by exploratory factor analysis. Multiple regression analyses found that student engagement in academic, youth development, and arts after-school program activities was significantly related to changes in teacher ratings of academic skills and social competence over the course of the school year and that students with the greatest increase in academic skills both were highly engaged in activities and attended the after-school program regularly. The results of this study provide additional evidence regarding the benefits of after-school programs and the importance of student engagement when assessing student outcomes.