The quality of our early attachment relationships with primary caregivers is carried forward to new developmental domains, including interpersonal contexts in adulthood. One of the factors that can disrupt early attachment is maternal depression, which may be associated with less responsive care and may impede the development of a secure attachment. Moreover, this disruption in secure attachment may act as a mechanism by which offspring of depressed mothers are more likely to experience their own psychopathology. In this study we predicted that attachment anxiety and avoidance would mediate the relationship between maternal depression diagnosis and functional impairment predicting young adult offspring's functional impairment.This study utilized longitudinal data from 98 families with clinically diagnosed depressed and well mothers, and two of their young adult children, an older and younger sibling (N = 123, Female = 75, Mage = 22.09, SD = 2.57). Mother's and young adult children's functioning was based on clinical ratings on the Global Assessment Scale. Attachment was based on the young adult's self-report on the Experiences in Close Relationships.Results indicate that maternal diagnosis and functional impairment predicted offspring's functional impairment. This relationship was partially mediated through offspring's attachment anxiety, but not attachment avoidance.The mediator and outcome variable were measured concurrently, thus causal implications are limited.Our study provides critical evidence that early experiences with depressed mothers may have influence into young adulthood in typical and atypical domains of development. This work extends our understanding of the impact of early experiences in long-term development, and may have treatment implications for intervening on both maternal and romantic relationships to improve attachment.