Background: Media use is associated with an increased risk of chronic disease and reduced quality of life among children. This study examined the relationship between media use during discretionary hours after school and psychological and physical assets among preadolescent girls. Methods: A cross-sectional analysis was conducted using data from a larger quasi-experimental evaluation of a positive youth development program through sport for third- to fifth-grade girls. Indicators of media use were the number of hours per school day spent watching television and videos and using computers. Psychological assets included global self-esteem, body size satisfaction, and commitment to physical activity; physical assets included physical activity. Nested random effects analysis of variance (ANOVA) models were used to examine the relationship between media use and psychological and physical assets controlling for relevant confounding factors. Results: The analytic sample included 1027 participants; most were [greater than or equal to]10 years old, non-White; 27% self-reported [greater than or equal to]4 hours of media use on school days. In adjusted results, media use was inversely associated with self-esteem (p = 0.008) and commitment to physical activity (p less than 0.001). Time spent using media was not associated with body size satisfaction or physical activity in this age group. Conclusions: Media use was negatively associated with self-esteem and commitment to physical activity. It may be useful for school professionals to encourage after-school programs that offer opportunities for girls to reduce sedentary pursuits and improve important psychological and physical assets. (Contains 2 tables.)