Culturally prescribed social scripts for traditional masculinity that emphasize social dominance are frequently linked to diminished well-being for men across a variety of psychological domains. However, few studies have examined the role of traditional masculinity scripts in the lives of early adolescent boys and girls, despite their relevance during this period and their potential developmental implications. To address this need, we examined the development of early adolescents' conformity to traditional masculinity across the middle school transition, as well as its links with depressive symptoms and academic engagement. Using a diverse sample of 280 adolescents (M (age) = 11.13, SD = 0.51; 54.3 % Female; 44 % Latina/o) assessed at the beginning (fall 2014) and end (spring 2015) of their first year of middle school, we found an increase in conformity to traditional masculinity scripts among boys, but not among girls. For boys and girls alike, conformity to traditional masculinity predicted greater depressive symptoms and decreased academic engagement. Depressive symptoms also mediated the association between traditional masculinity and academic engagement for boys and girls. This study is among the first to study conformity to traditional masculinity from a developmental lens. The findings suggest that traditional masculinity scripts are relevant for early adolescents (particularly boys) transitioning to middle school. However, for both boys and girls, conformity to these scripts can compromise psychological and academic well-being.