Youth spend substantial time on social media, which can foster self-critical processes that increase risk of body dissatisfaction, disordered eating, and depressed mood. To date, there have been few investigations of interventions to decrease the negative impacts of social media engagement in adolescent boys and girls. This paper outlines the protocol for a cluster randomized controlled trial (RCT) of a four-lesson social media literacy program that was developed based on pilot results and aims to decrease body dissatisfaction, dietary restraint, and strategies to increase muscles. The RCT will be conducted with grades 7-8 students from Australian secondary schools. Using block randomization, grade levels within schools will be assigned to either the SoMe program (intervention) or health lessons as usual (control). Primary outcomes will be body satisfaction, dietary restraint, and strategies to increase muscles. Secondary outcomes will be self-esteem and depressed mood. Participants will complete assessments on four occasions - baseline, five-weeks post-baseline, and six- and 12-month post-baseline. Analyses will compare outcomes in the intervention compared to the control group. This study will be the first to implement a RCT design to evaluate the impact of a school-based social media literacy program designed to mitigate negative impacts of social media.