This study investigated the socialization of children's emotion regulation in physically maltreating and non-maltreating mother-child dyads (N = 80 dyads). Mother-child dyads participated in the parent-child emotion interaction task (Shipman & Zeman, 1999) in which they talked about emotionally-arousing situations. The PCEIT was coded for maternal validation and invalidation in response to children's emotion. Mothers were also interviewed about their approach to emotion socialization using the meta-emotion interview-parent version (Katz & Gottman, 1999). The meta-emotion interview-parent version was coded for maternal emotion coaching. Mothers also completed measures that assessed their child abuse potential and abuse-related behaviors as well as children's emotion regulation. Findings indicated that maltreated children demonstrated fewer adaptive emotion regulation skills and more emotion dysregulation than non-maltreated children. In addition, maltreating mothers engaged in less validation and emotion coaching and more invalidation in response to children's emotion than non-maltreating mothers. Finally, maternal emotion socialization behaviors mediated the relation between maltreatment status and children's adaptive emotion regulation skills.