Children with histories of maltreatment and disruptions in care are at elevated risk for impairments in early language development, which contribute to difficulties in other developmental domains across childhood. Given research demonstrating associations between parent responsiveness and children's early language development, we examined whether a parenting intervention administered in infancy improved preschool receptive language skills in children involved with the child welfare system. Attachment and Biobehavioral Catch-up (ABC) is a 10-session intervention that aims to enhance parent-child interactions. The follow-up results of this randomized clinical trial demonstrated that infants who received the ABC intervention (n = 24) scored significantly higher on a test of receptive vocabulary at age 36 months than infants who received a control intervention (n = 28). These results provide evidence of the critical role of parental responsiveness in supporting optimal language development among young children with histories of child welfare involvement.