The purpose of the study was to analyze and describe the effect of performance appraisal and job characteristics on organizational commitment and their impact on employee performance. The population in this study were employees of  Tax Service Office (KPP) Madya Dua Semarang, amounting to 108 people. The sample in this study were employees of KPP Madya Dua Semarang. Sampling with the census sampling technique which is a sampling technique by taking all existing populations to be used as samples so that a sample of 108 respondents is obtained. The data collection method used a questionnaire while the data analysis used linear regression analysis and Sobel test.

Research results: (1). Based on the results of the instrument test, it is known that all indicators are valid and reliable. (2). Hypothesis testing proves that performance appraisal and job characteristics have a positive and significant effect on organizational commitment. Performance appraisal, job characteristics and organizational commitment together or simultaneously have a positive and significant effect on employee performance. (3) The mediation test proves that the effect of performance appraisal on employee performance is mediated by organizational commitment.

Keywords: performance appraisal, job characteristics, organizational commitment, employee performance.