Objective: Children exposed to early institutional rearing are at risk for developing psychopathology. The present investigation examines caregiving quality and the role of attachment security as they relate to symptoms of psychopathology in young children exposed to early institutionalization. Method: Participants were enrolled in the Bucharest Early Intervention Project (BEIP), a longitudinal intervention study of children abandoned and placed in institutions at or shortly after birth. Measures included observed caregiving when children were 30 months of age, observed attachment security at 42 months, and caregiver reports of children's psychopathology at 54 months. At 54 months, some children remained in institutions, others were in foster care, others had been adopted domestically, and still others had been returned to their biological families. Thus, the children had experienced varying amounts of institutional rearing. Results: After controlling for gender, quality of caregiving when children were 30 months old was associated with symptoms of multiple domains of psychopathology at 54 months of age. Ratings of security of attachment at 42 months mediated the associations between quality caregiving at 30 months and fewer symptoms of psychopathology at 54 months. Conclusions: Among deprived young children, high-quality caregiving at 30 months predicted reduced psychopathology and functional impairment at 54 months. Security of attachment mediated this relationship. Interventions for young children who have experienced deprivation may benefit from explicitly targeting caregiver-child attachment relationships. (Contains 4 tables and 1 figure.)