Girls and women are underrepresented in science, technology, engineering, and mathematics (STEM) fields. Research has investigated various explanatory factors (e.g., lack of role models, sexism) in these patterns. However, to date, the roles of media use and body concerns have not been examined. This study investigated associations among appearance-focused social media behaviors (e.g., posting photos), objectified body consciousness (i.e., body shame, body surveillance), and attitudes toward math and science (i.e., self-expectancy, task value, cost, future plans) in a sample of U.S. middle school girls (N = 243). Results demonstrated that body shame partially mediated associations between appearance-focused social media behaviors and math and science attitudes. These findings suggest that media use and body concerns have implications for girls' involvement in STEM fields.