Abstract: Shyness is a temperamental trait characterized by fear and anxiety in the face of novel social situations and self-consciousness in situations of perceived social evaluation. Empirical findings in Western societies indicated that shy children were prone to peer relationship problems, including peer victimization and rejection, as well as psychological maladjustment, including loneliness, low self-esteem and symptoms of depression. However, studies of Chinese children have yielded inconsistent findings. For instance, Chen and his colleagues found that shyness was associated with peer acceptance and positive school adjustment in Chinese children. In contrast, Schwartz and his colleagues found that shy Chinese children were disliked and victimized at school. The inconsistence among these results can be explained by the difference in the periods that these studies were conducted. More and more evidences have proved that shyness was associated with psychological maladjustment in the current urban area of China. Gender plays an important role in the prevalence and the implications of shyness. Drawing upon developmental theory of the importance of peer relationships in childhood and gender role stereotype theory casting males as traditionally more dominant/assertive and females as more passive/submissive, we proposed a mediated moderation model that may explain differences in the potential implications of shyness for boys and girls, which assumed that the relations between shyness and psychological adjustment were moderated by gender and the effects of gender were transmitted through peer relationship problems. Participants were N=1485 children (751 boys, 734 girls, Mage=11.25, SD=22 months) recruited from grade 3-8 classrooms in four randomly selected public schools in Shanghai. Assessments of shyness, peer victimization, peer rejection and psychological adjustment were obtained from multiple sources, including self-reports and peer nominations. Results indicated that: (1) there were significant gender difference on shyness, peer relationship problems and psychological adjustment. Girls had higher scores on shyness and self-esteem, but lower scores on peer relationship problems, loneliness and depression than did boys; (2) shyness was positively associated with peer relationship problems, loneliness and depression, but negatively associated with self-esteem; (3) the relations between shyness and psychological adjustment were moderated by gender. Shyness was more strongly associated with psychological maladjustment among boys as compared to girls; (4) the moderating effects of gender on shyness and psychological adjustment were mediated by peer relationship problems, the indirect effects made up 25% to 47% of the total effects. These results suggest that shy boys and girls are treated and responded to differently by peers, which leads to the gender differences in the outcomes of shyness. Gender plays an important role in the prevalence and the implications of shyness. Drawing upon developmental theory of the importance of peer relationships in childhood and gender role stereotype theory casting males as traditionally more dominant/assertive and females as more passive/submissive, we proposed a mediated moderation model that may explain differences in the potential implications of shyness for boys and girls, which assumed that the relations between shyness and psychological adjustment were moderated by gender and the effects of gender were transmitted through peer difficulties. Participants were N=1485 children (751 boys, 734 girls, Mage=11.25, SD=22 months) recruited from grade 3-8 classrooms in four randomly selected public schools in Shanghai. Assessments of shyness, peer victimization, peer rejection and psychological adjustment were obtained from multiple sources, including self-reports and peer nominations. Results indicated that: (1) there were significant gender difference on shyness, peer difficulties and psychological adjustment. Girls had higher scores on shyness and self-esteem, but lower scores on peer difficulties, loneliness and depression than did boys; (2) shyness was positively associated with peer difficulties, loneliness and depression, but negatively associated with self-esteem; (3) the relations between shyness and psychological adjustment were moderated by gender. Shyness was more strongly associated with psychological maladjustment among boys as compared to girls; (4) the moderating effects of gender on shyness and psychological adjustment were mediated by peer difficulties, the indirect effects made up 25% to 47% of the total effects. These results suggest that shy boys and girls are treated and responded to differently by peers, which leads to the gender differences in the outcomes of shyness.