A vivid scholarly debate addresses the extent to which social media usage is detrimental for adolescents’ mental health and body satisfaction. The current study aims to advance the debate in three ways: (1) we differentiate between different types of active and passive social media use (i.e., authentic vs. edited content), (2) we examine both between- and within-person results, and (3) we take a cross-national approach. Therefore, a three-wave panel study was conducted among 987 adolescents in Japan (N = 433) and the Netherlands (N = 554) to longitudinally investigate the relationships between active visual self-presentation, passive exposures thereto, and mental health and body satisfaction. Between-person results generally indicate that, regardless of being active or passive, both creating or seeing authentic content can be associated with increases in mental health and body satisfaction. Contrary, both creating and seeing edited content can coincide with reduced levels of mental health and body satisfaction. Nevertheless, the results should be seen in light of differences in between- and (lagged) within-person processes as well as cross-country differences. In all, evidence exemplifies the need for a communication-centered approach specifying content heterogeneity, showcases differences in between- and within-person effects, and demonstrates cross-national differential susceptibly to media effects.