This research aims to describe the influence of the school environment on teacher performance, the influence of teacher professionalism on teacher performance, and the influence of using the school environment and teacher professionalism together on teacher performance. Data collection uses questionnaires. Data analysis is quantitative/statistical using multiple linear regression. The research results show that the school environment has an influence on teacher performance. Teacher professionalism influences teacher performance where the correlation coefficient value of 0.921 indicates that teacher professionalism has a high and strong influence on teacher performance. The school environment and teacher professionalism simultaneously influence the performance of junior high school teachers in Girian District, Bitung City. The school environment and teacher professionalism simultaneously have a high contribution to teacher performance where R-square is = 84.5%. The results were strengthened based on the F test results which showed Fcount 252,652 > Ftable 3.11 with a significance value = 0.000 ˂ 0.05. This means that the better the condition of the school environment and the professionalism of teachers simultaneously, the better and the teacher's performance will increase.