Background <p>Young adults are increasingly affected by the experiences of disordered eating, body dissatisfaction, and problematic use of appearance-focused social media. However, little evidence exists, particularly for men, regarding the direction of these relationships or if they reciprocally predict change over time The present study aimed to address this gap and examine if appearance-focused social media use predicts exacerbation (increases) or maintenance (stability) of body dissatisfaction and disordered eating over 6-weeks, and whether the reverse occurs.</p> Methods <p>A sample of 488 men (<i>N</i> = 247) and women (<i>N</i> = 241) aged 18–30 (<i>M</i> = 26.50, <i>SD</i> = 2.96) were recruited through Prolific and completed an online survey at baseline and 6-weeks (T2).</p> Results <p>In univariate and multivariate logistic regression analyses, reciprocal predictors of exacerbation were observed; higher social media use predicted exacerbation (versus asymptomatic-stability) of body dissatisfaction and exacerbation of disordered eating, and higher disordered eating predicted exacerbation of use of social media. Body dissatisfaction was a significant predictor of social media use exacerbation in univariate analyses only. Reciprocal relationships were not observed for prediction of maintenance (versus cessation). Only gender predicted social media use maintenance in univariate analysis (women had higher odds of maintenance than men) and higher body dissatisfaction predicted maintenance of disordered eating in univariate and multivariate analyses.</p> Conclusion <p>Findings of small bidirectional prospective associations between appearance-focused social media use, body dissatisfaction, and disordered eating enhance understanding of the direction of relationships. This underscores the importance of addressing bidirectionality in prevention efforts and theories. Outcomes also suggest different factors may maintain, rather than predict these issues, warranting further investigation.</p>