This article reviews research examining the effects of adverse early caregiving on relationships throughout the lifespan. Central attachment constructs are summarized and integrated into a review of research on the long‐term effects of institutional rearing and child maltreatment. Findings are interpreted within the organizational perspective on development, which conceptualizes attachment as a stage‐salient task of infancy that influences the reorganization of adaptive/maladaptive functioning around subsequent stage‐salient tasks. Children who experience adverse early caregiving are more likely to exhibit aberrant attachment behaviors, deficits in social‐emotional competencies, and persisting difficulties in social functioning and relationship outcomes. Disorganized attachment behavior stemming from adverse early caregiving has been a major focus of this work. Intervention efforts that target mental representations related to attachment relationships can facilitate improved social functioning. Clinical implications of this work are discussed.