The present study examined whether teen mothers' adaptive cultural characteristics (i.e., familism values, language competency pressures, and involvement in Mexican culture and U.S. mainstream culture) when children were 3 years old (i.e., Wave 4; W4) informed mothers' Spanish language use with their children when children were 4 years old (W5) and, in turn, children's subsequent Spanish receptive vocabulary when children were 5 years old (W6). The present study included 204 Mexican-origin children (58% male) and their mothers who entered parenthood during adolescence (M = 16.24, SD = .99 at W1). Five mediational processes were significant, such that mothers' higher familism values (i.e., emphasizing family support and obligations), Spanish competency pressure (i.e., stress associated with Spanish language competency), and involvement in U.S. mainstream culture at W4 were associated with mothers' lower Spanish language use with children at W5 and, in turn, children's lower levels of Spanish receptive vocabulary at W6. Mothers' greater involvement in Mexican culture and English competency pressure (i.e., stress associated with English language competency) at W4 were associated with mothers' greater Spanish language use with children at W5 and, in turn, children's greater Spanish receptive vocabulary at W6. Additionally, mothers' greater involvement in U.S. mainstream culture at W4 was directly associated with children's lower Spanish language abilities at W6. Findings highlight the importance of the family context in Mexican-origin children's Spanish language skills over time. (PsycInfo Database Record (c) 2024 APA, all rights reserved).