Attachment theory states that experiences with primary caregivers influence other close relationships throughout the lifespan (Bowlby, 1969/1982). The quality of early caregiving experiences influences children’s mental representations of how others will treat them. These representations guide social information processing, the way that individuals remember, perceive, hold expectations, and make attributions about their social world. The present study is the first to examine how young adolescents’ attachment to parents influences their attribution biases about future romantic relationships. Attachment insecurity with mothers and fathers predicted negative attribution biases about hypothetical future romantic partners. Insecurity to fathers marginally predicted negative attributions above those predicted by insecurity to mothers. Negative attributions, in turn, predicted adolescents’ forecasting their own negative behaviors in a future relationship. Further, adolescents’ attachment avoidance (discomfort with closeness) across both parents predicted negative attributions. Results suggest that attribution biases could explain relations between attachment to caregivers and later romantic relationship functioning.