This study examined different individual, family factors and classroom environment that affect children's perceived competency. For an analysis, achievement motivation, intrinsic locus of control and anxiety were included in individual variables. For family factors, parental support and marital conflict were examined. For classroom psycho-social environment, teacher support, peer relations, classroom involvement and teacher control were used. The sample consisted of 565 fifth and sixth grade children. Statistics and methods used for the data analysis were Cronbach's alpha, Factor analysis, frequency, percentage, t-test, Pearson's correlation, and Hierarchical Regression. Several major results were found from the analysis. First, boy's perceived academic competency was higher than girl's. And no sex difference was in children's social and athletic competency. Second, boy's and girl's perceived academic and social competency and boy's perceived athletic competency had a positive correlation with achievement motivation, intrinsic locus of control, parental support, teacher support, peer relations and classroom involvement. And girl's perceived athletic competency had a positive correlation with achievement motivation, intrinsic locus of control, parental support and peer relations. But boy's and girl's perceived academic and social competency and boy's perceived athletic competency had a negative correlation with anxiety and parental marital conflict. Third, the most important variable predicting boy's and girl's perceived academic competency was achievement motivation. The most important variable predicting boy's and girl's perceived social competency was peer relations. And the most important variable predicting boy's perceived athletic competency was peer relations. On the other hand, the most important variable predicting girl's perceived athletic competency was father's support.