A majority of developmental psychologists have recognized that early adult-child relationship plays an important role in children's social development. Previous research on developmental psychopathology indicated that the mother-child relationship and teacher-child relationship both separately served as protective as well as risk factors in children's externalizing and internalizing problems. However, less attention has been given to how the mother-child and teacher-child relationships combine to influence children's emotional and behavioral adjustment. The aim of the present study was to investigate the separate as well as joint contributions of mother-child relationship and teacher-child relationship to children's internalizing and externalizing problems. Furthermore, since the present study focuses on preschool beginners, it also represents a specific program to identify the possible risk and protective factors that affect children's social adjustment during the transition from home to preschool. Based on a sample of 102 preschoolers aged 2 to 3 years and their mothers and teachers, the present study examined mother-child and teacher-child relationships in relation to these children's internalizing and externalizing problems in their first preschool years. Hierarchical regression analysis was applied to detect the separate effects of mother-child and teacher-child relationships on children's behavior problems as well as the moderation effect of teacher-child relationship on the relation of mother-child relationship to behavior problems. The results indicated that after controlling the effects of children's Time 1 behavior problems, the mother-child relationship was not a significant predictor of their Time 2 behavior problems, while teacher-child conflict could negatively predict children's Time 2 withdrawal and delinquency problems. The teacher-child relationship and child gender served to moderate the association between mother-child relationship and children's externalizing and internalizing problems, in that a positive association between mother-child conflict and children's aggression was found only in girls (simple slope = 0.83, t= 2.00, p 0.05) but not in boys. A high-quality teacher-child relationship predicted negative associations between mother-child closeness and children's withdrawal (simple slope = -0.48, t= 2.01, p0.05), anxiety (simple slope = -0.96, t= 2.68, p 0.01), aggression (simple slope = -1.03, t= 2.35, p 0.05), and delinquency (simple slope = -0.46, t= 2.37, p 0.05) problems, while a low-quality teacher-child relationship predicted no significant associations between mother-child closeness and children's withdrawal, aggression, and delinquency problems and a positive association between mother-child closeness and children's anxiety problem (simple slope = 1.06, t= 3.12, p 0.01). These findings highlight the importance of examining the continuity of adult-child relationship at home and at preschool in order to best understand children's emotional and behavioral adjustment and of expanding the existing research on parent-child relationship by underlying the importance of teacher's influence in the socialization process.