We examined the impact on adolescent socioemotional functioning of maternal postnatal depression (PND) and attachment style. We also investigated the role of earlier aspects of the child's development–attachment in infancy, and 5-year representations of family relationships. Ninety-one mother–child pairs, recruited in the postnatal period, were followed up at 13 years. Adolescents were interviewed about their friendships, and their level of emotional sensitivity and maturity were rated. Emotional sensitivity was heightened in girls whose mothers experienced PND; notably, its occurrence was also linked to insecure attachment in infancy and raised awareness of emotional components of family relationships at 5 years. High emotional sensitivity was also associated with adolescent depressed mood. Raised social maturity was predicted by a secure maternal attachment style and, for girls, by exposure to maternal PND. Precursors of adolescent social maturity were evident in the narrative coherence of 5-year family representations. Higher social maturity in the friendship interview was also associated with overall good adjustment.This research was supported by the Tedworth Charitable Trust and a Medical Research Council (UK) Program Grant. We thank Sheelah Seeley for her assistance with data collection; Peter Cooper for assistance with diagnostic interviews; and Claire Kempton, Mary-Sue Moore, and Gwen Adshead for assistance with the administration and scoring of the Adult Attachment Interview. Thanks also to Françoise Hentges and anonymous reviewers for comments on the manuscript and Kim Bailey for assistance with its preparation.