In the world of education, the principal is a leader who has a big role in improving teacher professionalism. The challenge of being a teacher is always moving dynamically, teachers must be able to adapt to technological developments by carrying out professional development consistently and continuously. This can be done by principals who apply transformational leadership. Transformational leadership is the ability of a leader to influence subordinates to achieve targeted goals to make changes that have a vision for the future and are able to identify environmental changes and are able to transform these changes into the organization, providing motivation and inspiration to their subordinates to be creative and innovative. Transformational leadership has a strong influence in running an organization. This study aims to determine the Implementation of Principal Transformational Leadership in Improving Teacher Performance in the Professional Field of Research Using a qualitative approach with the type of case study research and descriptive. The research location is at SMK Al Manar Pamarican and SMK Tri Bintang Purwadadi, Ciamis Regency. Collecting data through observation, questionnaires or questionnaires, interviews and documentation. Informants in this study were principals, educators, education staff and class XI students at SMK Al Manar Pamarican and SMK Tri Bintang Purwadadi Ciamis Regency. The results of the research on the leadership of the school principal have a significant influence on teacher performance, there is a significant influence on work motivation on the performance of teachers from the two vocational schools in Ciamis Regency.