The present study investigated the effects of situational (child situational emotions) and dispositional (child temperament) child variables on mothers' regulation of their own hostile (anger) and nonhostile (sadness and anxiety) emotions. Participants included 94 low and middle income mothers and their children (41 girls; 53 boys) aged 3 to 6 years. Children's situational emotions (anger, sadness, or fear) and parent emotion type (hostile or nonhostile) were important predictors of mothers' regulation, but their effects were influenced by SES: Middle income mothers were more likely to control hostile than nonhostile emotions in response to child anger and sadness, and more likely than low income mothers to control hostile emotions in response to child sadness and fear. Low income mothers were more likely than middle income mothers to control nonhostile emotions in response to child anger. However, results also suggest that differences in emotion regulation between low and middle income mothers may stem from the link between SES and authoritarian parenting beliefs. Maternal regulation of negative emotion was not predicted by child temperament.