This 3-year longitudinal study examined the extent to which body weight contingent self-worth (CSW) predicted depressive symptoms in 439 adolescent girls and the roles of unstable self-esteem and interpersonal sexual objectification in this association. Half-longitudinal mediation showed that the indirect effect of body weight CSW on depression via instability of self-esteem was significant. Prior levels of body weight CSW predicted increases in unstable self-esteem, which predicted increments in depressive symptoms over time. However, earlier levels of depression did not significantly predict increases in self-esteem instability. Moderation analyses indicated that the indirect effect was conditional upon individuals’ experience of interpersonal sexual objectification. The positive link between body weight CSW and unstable self-esteem was stronger in girls who experienced more interpersonal sexual objectification. The direct effect of body weight CSW on depression was also moderated by interpersonal sexual objectification. Taken together, basing self-worth on body weight appears to be a risk factor for depression through its association with unstable self-esteem in adolescent girls and sexually objectifying experiences serve to exacerbate the connection between body weight CSW and adverse outcomes.