The main purpose of this study was to determine the opinions of the teacher candidates who attend the pedagogical formation certificate programme for the professional competency of instructors. The method of the research is a descriptive survey based on scanning. The study group included the teacher candidates who attend the pedagogical formation certificate programme organized in Cankiri Karatekin University. In order to collect the data of the research, "Scale of Professional Competency of Instructors (OEMYO)" was developed. The professional competencies were classified into 5 main sections and in each section, totally 50 behaviours are determined. For five sub-sections of OEMYO, validity study was done separately with factor analysis. The construct validity of each professional competency is determined by descriptive factor analysis. Research data were analysed by applying t-test, Kruskal Wallis-H test and Mann Whitney U test as well as descriptive statistics. In this research, it was determined that the instructors constantly perform the professional competencies during study period. There was no significant difference in the views of teacher candidates related to developing professional competence of instructors according to their education levels and when they graduated. On the other hand, there were significant differences in certain professional competencies according to the gender of the teacher candidates and the departments they graduated from. (Contains 10 tables.)