The current study took a developmental and familial perspective to understand the impact of bicultural management difficulties on internalizing symptoms within mother-adolescent dyads. Multilevel analyses were conducted based on a three-wave data set from 604 adolescents (54% female; Mage = 12.92) and their mothers (n = 596; Mage = 38.89) in Mexican immigrant families collected from 2012 to 2020. Higher average levels (i.e., between-person) and fluctuations (i.e., within-person) in bicultural management difficulties during adolescence were risk factors for internalizing symptoms for both adolescents and their mothers. Moreover, the between-person average level of bicultural management difficulty in a partner (adolescent or mother) moderated the within-person association between fluctuations in one's own bicultural management difficulties and their own anxiety symptoms.