The performance of a teacher can be influenced by several factors. Among the factors that can affect teacher performance are the leadership of the principal, the competence of the teacher himself, and the teacher's motivation in carrying out his duties. This study aims to analyze whether there is a significant influence between the principal's leadership, competence, and motivation on teacher performance either simultaneously or partially. The design of this research is quantitative with ex post facto design. This study is looking for systematic empirical data and in this study the researcher cannot directly control the independent variables because the events have occurred and according to their nature cannot be manipulated. The population in this study were high school teachers in Mamasa district, data collection using instruments. Data analysis used multiple linear regression with the help of a computer program SPSS 22.00 for Windows. The results of the study simultaneously show that the principal's leadership, competence, and motivation affect teacher performance. Partially, the competence possessed by teachers has an effect on teacher performance, but the principal's leadership and motivation have no effect on teacher performance. Therefore, to improve performance, teachers should increase their competence, one of the ways is by continuing their education to a higher level. On the other hand, the principal must apply an effective leadership style and always motivate teachers to always develop their competence.