The main goal of this study was to investigate the differences between the pre-service and in-service teachers in terms of their levels of teaching efficacy and teaching professionalism. The participants were 593 teachers in Korean Early Childhood Education and Care.They were divided into two subgroups consisting of pre-service teachers and in-service teachers who had agreed to participate in the study. The results found that in-service teachers had higher scores than their counterparts in only one of the six subscales of teaching efficacy, which is the subscale “Teaching Strategies”. Furthermore, the results showed that the subject’s college major specialisation and some domains of professionalism were found to be predictive to both groups.