Appearance activity on social media can significantly amplify body dissatisfaction in adolescents. This study uses three-wave longitudinal data from 2,500 adolescents aged 11 to 16 (M = 13.4, SD = 1.7, 50% girls) to explore the associations between social media appearance activity, comparison with social media appearance ideals, internalization of these ideals, and body dissatisfaction. While significant between-person correlations were found over time, at the within-person level, heightened appearance activity did not increase body dissatisfaction in subsequent waves. Although heightened internalization of social media ideals predicted more appearance activity and appearance comparisons, these effects were not consistent across waves. Hence, this study indicates that appearance-related activities on social media do not necessarily reinforce body dissatisfaction in adolescents, providing insights for research and policy in this area.