Evidence documents the importance of individual differences in masculinity ideology for men's biological, social, and psychological wellbeing. Studies investigating the developmental antecedents of masculinity ideology and how it changes during specific developmental phases, however, are scarce. The present study examined the influence of childhood adversity and socioeconomic instability on Black men's masculinity ideology during emerging adulthood. Specifically, we investigated changes in two types of masculinity ideology: (a) respect-based, which is associated with prosocial outcomes such as hard work, education, and fidelity, and (b) reputation-based, which is related to antisocial outcomes such as sexual prowess, toughness, and authority-defying behavior. Hypotheses were tested using structural equation modeling with three waves of data from 504 Black American men aged 19 to 22 at baseline living in resource-poor communities in the rural South. Results indicated that childhood adversity was associated with elevated socioeconomic instability during emerging adulthood. Childhood adversity and socioeconomic instability were associated with decreases in respect-based masculinity and increases in reputation-based masculinity. Indirect effects were detected whereby childhood adversity was associated with respect-based and reputation-based masculinity indirectly via socioeconomic instability. Taken together, these results suggest that childhood adversity and socioeconomic instability forecast changes in the types of masculinity ideology rural Black men endorse during the emerging adulthood transition.