Infants in foster care need sensitive, responsive caregivers to promote their healthy outcomes. The current study examined the effectiveness of the Attachment and Biobehavioral Catch-up Intervention, a short-term, targeted, attachment-based intervention program designed to promote sensitive caregiving behavior among foster mothers. Ninety-six foster mother-infant dyads participated in this study; 44 dyads were assigned to the Attachment and Biobehavioral Catch-up Intervention, and 52 dyads were assigned to a control intervention. Results of hierarchical linear modeling indicated that foster mothers who were assigned to the Attachment and Biobehavioral Catch-up Intervention showed greater improvements in their sensitivity from pre- to postintervention assessment time points when compared with foster mothers who were assigned to the control intervention. We conclude that a short-term, targeted, attachment-based intervention is effective in changing foster mothers' responsiveness to their foster infants, which is critical for foster infants' healthy socioemotional adjustment.