Abstract Background Maternal depression is known to be a risk for abnormal child development. Girls and boys have been found to respond differently to maternal depression. Although prenatal and postnatal depression has been widely studied, longitudinal studies of adolescent outcome are still rare. Methods The original sample of 349 mothers in this longitudinal study was collected in 1989–1990 in Tampere, Finland. At the latest stage, of the 327 contacted in 2006, 191 mothers and 192 adolescents aged 16 to 17 years participated in the study. Maternal depressive symptoms were screened using the Edinburgh Postnatal Depression Scale (EPDS) prenatally, postnatally and at the latest stage. Adolescent outcome was examined using the Child Behavior Checklist (CBCL) and the Youth Self Report (YSR). Results Maternal concurrent depressive symptoms were associated with adolescent behavioral and emotional problems in both genders. Maternal prenatal depressive symptoms were associated with Externalizing Problems in the YSR and boys' lower Social Competence in both the CBCL and YSR. Maternal postnatal depressive symptoms were associated with boys' lower Social Competence both in the CBCL and YSR and Externalizing Problems in the YSR. Limitations Being a longitudinal normal population sample, the number of symptomatic mothers and adolescents is relatively small and the number of drop-outs is relatively high. Clinical evaluation of mothers and adolescents is also lacking. Conclusions Maternal prenatal and postnatal depressive symptoms are a risk to adolescent boys' wellbeing and concurrent depressive symptoms a risk for both girls' and boys' well-being. This long-term influence should be noted when treating women with depressive symptoms throughout motherhood.