The current study focused on the relationship between body dissatisfaction and depressive symptoms on the threshold of adolescence. We aimed to investigate the role of body dissatisfaction in gender differences in depressive symptoms, as well as the impact of social support from peers and parents. Mediation and moderation analyses were based on self-reports from a Norwegian population-based sample (the Tracking Opportunities and Problems Study) of 12- to 13-year-olds (N = 547). Body dissatisfaction explained over 20% of the variance in depressive symptoms. The findings indicate that body dissatisfaction mediates gender differences in depressive symptoms, and that peer support moderates the positive association between body dissatisfaction and depressive symptoms. This is in line with Stress Exposure and Stress-Buffering models. The findings indicate that to prevent depressive symptoms in the transition into adolescence, focus should be on promoting body satisfaction, especially in girls, as well as promoting peer support for adolescents already struggling with body dissatisfaction.