This study aims to examine the effect of principal leadership, teacher attitude, teacher competence on teacher performance at SMK Negeri 3 Pematangsiantar, either partially or simultaneously. The sample in this study were teachers of SMK Negeri 3 Pematangsiantar totaling 98 people. The data in this study are primary data. The data were collected using a questionnaire. The analytical method used is the Multiple Linear Regression model. To test the hypothesis simultaneously the F test is used and partially the t test is used. The results of the tests carried out with SPSS obtained multiple regression equations: Y = 10.857 + 1.084 X1 + 0.144 X2 + 0.232 X3, which means a constant value of 10.857 which indicates that if the principal's leadership, teacher attitudes and teacher competencies are assumed to be zero, then the value is zero. of the teacher's performance is equal to 10,857. If the independent variable increases by 1%, the teacher's performance will increase. The results of the t-test hypothesis of the research variable are the principal's leadership variable obtained tcount8,691 with a significant probability of 0.000 less than the level of confidence (level of significant) = 0.05, the teacher's attitude variable is obtained tcount2.753 with a significant probability of 0.007 smaller than the level of confidence (level of significant) = 0.05. The teacher competency variable was obtained tcount 3.807 with a significant probability of 0.000 less than the level of confidence (level of significant) = 0.05. So the decision taken is to reject H0 and accept Ha, meaning that the principal's leadership, teacher attitudes, teacher competence have a positive and significant effect on the performance of teachers at SMK Negeri 3 Pematangsiantar