Gender expression is important for mental health, with masculinity and femininity having differential significance for unique adolescents. Yet, most empirical work on gender expression assumes it is trait-like or similarly shifting across teens. This intensive longitudinal study examined state-like aspects of gender expression and heterogeneity in adolescent-specific associations with depressive symptoms over 100 days. Participants were 106 adolescents, including 5 gender-expansive youth (54.7% cisgirls, 74.5% White; M = 13.31, SD = 1.94). A sample-average link between daily masculinity and reduced symptoms was found for cisboys. Adolescent-specific results qualified this effect: Only ~25% evidenced an association between daily gender-congruent expression-masculinity for cisboys and femininity for cisgirls-and daily reduced symptoms. Using 9000+ daily reports, findings highlight the dynamic nature of gender expression and the need to use a person-specific approach in understanding the heterogenous psychological correlates of masculinity and femininity for today's youth.