This study aims to describe how the implementation of clinical supervision carried out by junior high school principals improves teacher performance at SMPN 1 Leuwigoong Public Middle School in Garut District. The subjects of this study were the principal, teachers, and staff of SMPN 1 Leuwigoong. The results showed that the clinical supervision that had been carried out by the school principal for teachers was good, although it had not been carried out according to the procedures for implementing good clinical supervision. Clinical supervision carried out at least had a good impact on teachers in terms of their ability to carry out learning and on staff in terms of school management. All the methods used by school principals are able to improve the teaching skills of teachers and school management for staff.