Appearance pressure from mass media and appearance social comparisons have been implicated in theory and research on disordered eating. However, mediating effects of upward and downward appearance comparisons on associations between appearance pressure and changes in disordered eating among women versus men have not been examined within longitudinal research designs. To address this gap, undergraduate students (1539 women and 882 men) from China completed self-report measures of appearance pressure from mass media; upward and downward appearance comparisons with more and less physically attractive peers, respectively; and disordered eating at baseline and/or a 12-month follow-up. Analyses indicated that, after controlling for gender differences on demographics and initial levels of disordered eating, baseline pressure from mass media contributed to the prediction of disordered eating at follow-up within each gender. Among women, in particular, follow-up upward appearance comparisons with peers mediated this association. For men but not for women, downward appearance comparisons with peers emerged as a significant mediator. Findings underscored differential relations of appearance comparisons with exacerbations in disordered eating among women versus men and suggested that associated interventions might be tailored on the basis of gender.