The main purpose of this study was to investigate the differences between pre-service and in-service teachers in terms of their levels of teaching efficacy and teaching professionalism. In addition, the patterns in predictors of teachers' teaching efficacy were compared between the two subgroups of this study. Five hundred and seventy-three teachers completed self-administered questionnaires. The in-service teachers were found to have higher efficacy than their counterparts in only one of the six subscales of teaching efficacy, the subscale "Teaching Strategies". Additionally, the college major specialisation and some domains of professionalism were found to be predictive to both groups. Along with the main results of this study, implications for research and practice are discussed.