Despite the potential of peers to reinforce cultural appearance ideals, little work on peer media co-viewing has focused on body image. This study therefore examined relationships among peer television co-viewing, perceptions of media as important appearance-related information sources, and internalization of media appearance ideals. Adolescents aged 10–14 were included (Study 1: N = 363, Mage (SD) = 12.30 (0.86), 56.5% female; Study 2: N = 959, Mage (SD) = 11.17 (1.11), 48.9% female). Evidence emerged for a positive cross-sectional relationship between peer television co-viewing and media internalization, via media credibility. However, longitudinally, among adolescents reporting frequent media-related peer conversations, peer television co-viewing was negatively associated with media credibility. Peer co-viewing and mediation may be implicated in appearance-related beliefs among adolescents.