Managerial ability is very important for school principals. So that it is able to compete with its competitors and produce quality graduates and it is realized that now the world of education is growing with technology. The principal does not limit communication with all school members, including teachers as their subordinates. This study used a descriptive qualitative approach and was conducted at SMP Plus Al-Ittihad Selaawi. The subject of this research is the principal as primary data and teachers as secondary data. Data collection techniques used in this study were observation, interviews and documentation studies. Data analysis used in this research is preparation, tabulation, and application. The validity of the data used is the credibility, transferability, dependability and certainty of the data. The results of this study indicate that the application of managerial skills for school principals in improving teacher professionalism is carried out well. The principal's managerial competence has a complementary relationship with each other. The principal always provides guidance and direction in teacher performance, this guidance and direction is an effort to improve teacher professionalism. In addition, school principals provide guidance and also develop teacher professionalism by directing teachers to attend technology guidance, workshops, seminars and MGMPs. The principal also always monitors and evaluates the performance of teachers to determine their professional achievements