Parent-child attachment security and dyadic measures of parent-child positive and negative emotional reciprocity were examined as possible mediators and moderators of the connection between marital conflict and children's peer play behavior. Eighty parents were observed in a laboratory play session with their 15- to 18-month-old child. Subsequently, at 36 months children were observed interacting with peers at their child care setting. Connections between marital conflict and children's positive peer interaction were mediated by mother-child attachment security, mother-child positive emotional reciprocity, and father-child negative emotional reciprocity. Connections between marital conflict and children's negative peer interaction were mediated by mother-child positive emotional reciprocity and father-child attachment security. Parent-child attachment security and negative emotional reciprocity emerged as important moderators of the connection between marital conflict and children's peer play behavior.