Objective: This study investigates the main effects and interaction effects of mother's reactions to young children's negative emotions on the children's problem behaviors. Methods: A total of 346 mothers with toddlers completed questionnaires, the data were analyzed using Pearson's correlation coefficient and multiple regression. Results: First, mothers’ supportive response to young children’s negative emotions, including expressive encouragement, emotion-focused reactions, and problem-focused reactions, showed negative relations with the children’s internal and external problem behaviors. Mothers' unsupportive response to children’s negative emotions, including distress reactions, minimization reactions, and punitive reactions, showed positive relations with the children’s internal and external problem behaviors. Second, an interactive effect was observed. For external problem behavior, mothers' lower distress reactions accompanied by higher emotion-focused reactions, lower punitive reactions accompanied by higher emotion-focused reactions, lower distress reactions accompanied by higher problem-focused reactions, and lower punitive reactions accompanied by higher problem-focused reactions all decreased children′s problem behavior. However, for internal problem behavior, only mothers' lower distress reactions accompanied by higher emotion-focused reaction decreased children′s problem behavior. Conclusion/Implication: The main interaction effect on mothers’ reaction to young children’s negative emotional expression shows that preventive intervention is needed to address problem behavior.