Objectification theory posits that the socialization of girls to self-objectify and monitor their bodies contributes to negative emotional experiences (e.g., body shame), and consequent psychological phenomena that disproportionately impact women (e.g., disordered eating, physical activity avoidance). Self-objectification may also be extended to the anticipation of negative emotions when thinking about changes to one's body in the future. Since self-objectification is heightened during adolescence, it is possible that it may lead to the decreased physical activity engagement that is observed in girls during this developmental period. The present study examined the role of body surveillance and body shame on physical activity among adolescent girls. Physically active girls (n = 201; Mage = 14.02 ± 1.38 years, MBMI = 19.78 ± 2.82) reported body surveillance at baseline, and their current and anticipated bodily shame, and physical activity 2 years later. Although body surveillance was not prospectively linked to physical activity, both anticipated (B = 0.059, CI = 0.003 to 0.131) and current body shame (B = -0.121, CI = -.211 to -.046) mediated the relationship between body surveillance and physical activity (R2adj=0.17). As expected, body surveillance increased both the experience and anticipation of body shame. Further, the experience of body shame was associated with the avoidance of physical activity, whereas the anticipation of shame was linked with higher engagement, presumably to avoid feeling shame in the first place. Extending objectification theory to include anticipated shame may be a promising avenue for exploring physical activity disengagement among adolescent girls.