This study examined the relations among toddlers' temperament, maternal parenting, and toddlers' social withdrawal and aggression. One hundred and two mothers of two-year-old children (49 boys and 53 girls) completed questionnaires and Q-sort. Data were analyzed by correlation analyses and regression analyses. First, toddlers' pleasure was negatively related to social withdrawal, while social fearfulness was positively related to social withdrawal. Also, toddlers' activity level and anger proneness were positively related to aggression. Second, the encouragement of independence in maternal parenting was negatively linked to toddlers' social withdrawal, and maternal rejection was positively linked to toddlers' aggression. Third, toddlers' pleasure and interest/persistence were positively associated with mothers' encouragement of independence, and toddlers' activity level and anger proneness were positively associated with mothers' rejection. Finally, mothers' encouragement of independence acted as a mediator between toddlers' pleasure and social withdrawal. Also, toddlers' activity level and anger proneness influenced aggression through maternal rejection. These results indicate that toddlers' temperament and maternal parenting play crucial roles in the development of toddlers' maladaptive behaviors such as social withdrawal and aggression.