We examined whether maternal emotion coaching at pretreatment predicted children's treatment response following a 12-week program addressing children's oppositional defiant disorder (ODD) symptoms. A total of 89 mother–child dyads participated. At pretreatment, mothers and children engaged in an emotion talk task. Mothers also reported their beliefs about emotions at pretreatment and their child's disruptive behavior symptoms, emotion regulation, and emotion lability/negativity at pre-, mid-, and post-treatment. Clinicians reported children's symptom severity at pre- and post-treatment. Children's emotion lability/negativity moderated effects of maternal emotion coaching on children's post-treatment ODD symptoms, with stronger benefits of emotion coaching for children high in emotion lability/negativity. Results suggest that emotion coaching may promote treatment response for children with ODD who are especially at risk due to their emotionality.