This study aimed to examine the degree to which elementary school teachers' perceived pre-service and in-service teacher helped their job performance as well as their professionalism and furthermore to examine the associations of these perceptions on their overall sense of professionalism. The data for this study were derived from 905 survey responses collected from elementary school teachers during the first phase of the Seoul Education Longitudinal Study of Teachers 2020 (SELST 2020). Descriptive statistical analysis revealed that elementary teachers generally showed modest scores on the perceptions of pre-service teacher education, with most responses scoring 3 or higher, except for the teaching and learning aspect. In contrast, their perceptions of in-service teacher education were more favorable, with scores over 3.7. Overall, elementary teachers reported moderately high levels of professionalism, averaging in the mid-5 on a 7-point scale. To examine the impact of pre-service and in-service teacher education on elementary teachers' perceptions of professionalism, a multiple regression analysis was conducted. The findings indicated that in-service teacher education was significantly associated with all dimensions of professionalism, whereas pre-service teacher education had a significant impact only on student assessment and daily guidance and counseling professionalism. Furthermore, variables such as teaching experience, gender, and whether or not teachers participated in professional learning communities in or out of schools were found to have significant effects on their perception of professionalism. Furthermore, school culture and climate emerged as significant factors influencing teachers' perceptions of professionalism. Based on the study's results, recommendations were formulated regarding the role and conditions of pre-service and in-service teacher education in order to establish and improve teachers’ professionalism during teachers’ career duration.