This study investigated the bidirectional relationships of adolescents' and maternal mood, and the moderating effect by gender and perceived family relationships on these relationships. Data were obtained from 626 adolescent-mother dyads and follow-up data were collected one year later from a subset. Adolescents reported their depressive symptoms, and their mothers reported their negative affect. Adolescents described their perception of family relationships. Maternal negative affect and adolescents' depressive symptoms were significantly correlated at baseline. This association was moderated by gender and family relationships. The association was stronger in mother-daughter compared to mother-son dyads. In families where relationships were reported to be poor, adolescent depressive symptoms were uniformly high, regardless of maternal negative affect. However, in families where relationships were good, maternal negative affect was associated with higher adolescents' depressive symptoms. In longitudinal analyses, adolescents' mood at baseline was found to relate to maternal negative affect at follow-up. Family relationships at baseline were also associated with adolescents' depressive symptoms at follow-up. However, there was no prediction from maternal negative affect at baseline to adolescents' depressive symptoms at follow-up. Gender and quality of family relationships did not moderate the longitudinal relationships between adolescents' depressive symptoms and maternal negative affect in either direction.