This study aimed to develop a measurement tool to determine the job performance perceptions of school principals based on their own competence. The list of School Principals Standards developed for the study of the Organization for Economic Cooperation and Development [OECD] has been used in many OECD countries but has not been used in Turkey and there is no study adapted to the Turkish Education System. In addition, since the list of School Principals Standards is not in a questionnaire or a scale form, and there is no scale that examines the school principals’ own perceptions of their performance based on their competencies, therefore the development of such a scale is aimed in this study. First, the list of School Principals Standards was adapted to Turkey, and then the items of the scale to be developed were written by taking expert opinions. The scale development was carried out with a process consisting of eight stages, and the suitable scale for the Turkish Education System was developed. The scale called “School Principals’ Competency-Based Job Performance Perceptions Scale” firstly was administered to 182 participants for the validity, reliability, and Explanatory Factor Analysis (EFA) of the scale, and then secondly administered to other 145 participants for the Confirmatory Factor Analysis (CFA). It was determined that the reliability level of the scale was high with the Cronbach α (0.959) coefficient. As a result of the EFA, a six-dimensional scale consisting of 41 items was obtained. The variance explanation rate of six factors was calculated as 59.66%. It has been determined that the goodness of fit values for the model determined as a result of the CFA performed to test the construct validity of the factor structure obtained provide good and sufficient criteria. The results obtained prove that the scale is valid and reliable.