This study examined the effects of child developmental knowledge, attribution, social support, and burnout on childcare teacher's professionalism. The participants were 985 childcare teachers in Incheon Metropolitan City and Gyonggi Providnce. The research instruments were Knowledge about Child Development Scale by MacPhee(1981), Attribution Scale by Levenson(1981), Social Support Scale by Park(1985), Burnout Scale by Maslach & Jackson(1986), and Childcare Teacher's Professionalism Scale by Lindsay & Lindsay(1987). Collected data were analyzed by t-test, F test and Scheff? test for post hoc test, Pearson's correlation, and simultaneous muitlple regression. The results were as follows: First, childcare teacher's knowledge about development, attribution, social support, burnout, and professionalism were above the average. Second, a perceived level for teacher's professionalism was correlated with the childcare teacher's knowledge about development, attribution, social support, and burnout. Third, among variables, internal responsibility of attribution was the best predictor of the teacher's professionalism. This provides practical suggestions for the Korean childcare policy and system.