This study aims to determine the effect of the work environment and organizational commitment on employee performance with job satisfaction as a mediating variable at the PT POS Indonesia processing center office. The research subjects were employees of the PT POS Indonesia processing center office located on Jl. Plemburan No.7, Sedan, Sariharjo, Ngaglik, Sleman Regency, Special Region of Yogyakarta 55581. Samples taken were 100 people. The sampling technique used was purposive sampling. The method of analysis in the study was Structural Equaation Modeling (SEM) using AMOS 24.00 software. Based on the analysis that has been carried out, the results show that: 1) the work environment has a negative effect on employee performance, 2) the work environment has a positive and significant effect on employee performance with job satisfaction as a mediating variable, 3) the work environment has a positive and significant effect on job satisfaction, 4 ) organizational commitment has a negative effect on employee performance, 5) organizational commitment has a positive and significant effect on employee performance with job satisfaction as a mediating variable, 6) organizational commitment has a positive and significant effect on job satisfaction and 7) job satisfaction has a positive and significant effect on employee performance