International marriages between Korean men and foreign women from other Asian countries have been increasing since the late 1990s in Korea. This study examines the mediating effects of parenting self-efficacy, career-specific parenting behaviors, and school adjustment on the relationship between immigrant mothers’ acculturative stress and their adolescent children’s career decidedness. Data were collected from 1181 third grade students (583 boys, 598 girls) in Korean middle schools and their foreign mothers who participated in the Multicultural Adolescents Panel Study. A structural equation modeling analysis revealed the following multiple mediation process: immigrant mothers’ acculturative stress is indirectly related to their adolescent children’s career decidedness through (1) the dual mediation of parenting self-efficacy and career-specific parenting behaviors; (2) the serial mediation of parenting self-efficacy, career-specific parenting behaviors, and adolescents’ school adjustment; (3) the dual mediation of parenting self-efficacy and adolescents’ school adjustment; and (4) the mediation of adolescents’ school adjustment. This study provides directions for parent education and career counseling to enhance immigrant mothers’ parenting competence and support the positive career development of adolescents from multicultural families. The study, therefore, helps them grow into well-adjusted adults in Korean society, which, in turn, contributes to the well-being of immigrant mothers and their adolescent children.