BACKGROUND: Adolescent depression is increasing globally, and family conflict may contribute to its transmission across generations. However, longitudinal evidence on these dynamics remains sparse. This study examines the longitudinal associations between family conflict and adolescents' and parents' depressive symptoms from three waves of data. METHODS: Data from the 2016-2020 China Family Panel Studies (CFPS) were analyzed, including 1,772 adolescents (Mean age = 12.4, SD = 1.68 in 2016) and their parents. Family conflict was measured using three questions from adolescents, while depressive symptoms were assessed using the Center for Epidemiological Studies Depression Scale (CESD). Multiplelinear regression, latent growth models (LGM), and cross-lagged panel models (CLPM) were employed to examine longitudinal associations between family conflict and depressive symptoms. RESULTS: The results revealed that family conflict correlated with adolescents' depressive symptoms (r = 0.580,p <
0.001). Adolescents' depressive symptoms also exacerbated family conflict (β1 = 0.030, p <
0.05
β2 = 0.032, p <
0.01) across three waves, while family conflict had a limited contribution to parents' depressive symptoms. Mothers' depressive symptoms influenced adolescents' depressive symptoms significantly (β = 0.043,p <
0.05), while adolescents' depressive symptoms were transmitted to fathers' depressive symptoms (β = 0.080,p <
0.01) between Wave 2 and Wave 3. Moreover, the mother's education level negatively predicted adolescents' depressive symptoms (β = -0.296,p <
0.05). CONCLUSIONS: Family conflict plays a critical role in adolescents' depressive symptoms and its intergenerational transmission. The findings underscore the pivotal role of family dynamics in mental health, especially in the development of adolescents' depressive symptoms. Interventions aimed at reducing family conflict may help mitigate depressive symptoms across generations.