This longitudinal study (N = 730) explored whether the three-step process of self-objectification (internalization of appearance ideals, valuing appearance over competence, and body surveillance) could explain the influence of sexual media messages on adolescents' sexual behaviors. A structural equation model showed that reading sexualizing magazines (Time 1) was related to the internalization of appearance ideals and valuing appearance over competence (Time 2). In turn, the internalization of appearance ideals was positively associated with body surveillance and valuing appearance over competence (all at Time 2). Valuing appearance over competence was also positively associated with body surveillance (all at Time 2). Lastly, body surveillance (Time 2) positively related to the initiation of French kissing (Time 3) whereas valuing appearance over competence (Time 2) positively related to the initiation of sexual intercourse (Time 3). No significant relationship was observed for intimate touching. The discussion focused on the explanatory role of self-objectification in media effects on adolescents' sexual behaviors.