The heuristic model of emotion socialization (Eisenberg et al., 1998; Eisenberg, 2020) identifies predictors of emotion-related parenting practices, such as children’s temperament, parent personality and emotion-related beliefs, and cultural factors. Though relations between the temperaments of mothers and their children have been studied, little is known about the interaction of child and parent temperaments and how this relates to children’s emotional development (Lewis, 2014). We examined how patterns of mother-child temperament were related to mothers’ emotion-related socialization (e.g., coaching, rejecting). We hypothesized that the relation between these mother-child temperament patterns and children’s emotion regulation would be mediated by maternal emotion-related socialization. Participants included an ethnically diverse sample of mothers (N = 168) living with young children (4-7 years old; 86 boys, 82 girls). Through a cluster analysis, dyadic mother-child temperament patterns were identified. Maternal emotion coaching and emotion rejecting were assessed using a self-report questionnaire of emotion-related socialization. Although maternal emotion coaching was not a significant mediator in models predicting emotion regulation, there was an indirect effect of temperament pattern on children’s emotion regulation through mothers’ emotion rejecting. Mother-child temperament patterns low in negative affectivity predicted lower emotion rejecting, and lower emotion rejecting predicted greater emotion regulation in children, even after accounting for covariates. In addition, mother-child temperament patterns had a direct effect on children’s emotion regulation. This study highlights associations between maternal emotion-related socialization, mother-child temperament patterns, and children’s emotion regulation.