The purpose of this exploratory study was to examine change in internalizing symptoms from late childhood (age 10) into mid-adolescence (age 15) in a nationally representative sample of Canadian children. The roles of a child's sex, maternal depressive symptoms in late childhood, and their interactions were investigated. The sample was derived from the National Longitudinal Survey of Children and Youth. Mothers reported on their own depressive symptoms and children reported on their own internalizing symptoms at three time (T) points (T1: 1994/1995; T2: 1996/1997; T3: 1998/1999). Change in children's internalizing symptoms was investigated using multiple regression. Girls increased and boys decreased in their internalizing symptoms from T1 to T3. The effect of maternal depressive symptoms at T1 was moderated by sex and remained significant after controlling for maternal depressive symptoms at T2 and T3, with more adverse effects in girls. The internalizing symptoms of girls increased from childhood to adolescence, whereas those for boys decreased. Female children exposed to maternal depressive symptoms T1 continued to show negative effects 4 years later.