This study aims to analyze the influence of servant leadership toward knowledge sharing behavior mediated by affective commitment. The information gained from this research is very important for the institution as a consideration for implementing the improvement of teacher performance through knowledge sharing behavior. Subjects in this study were teachers at the Institute of Integrated Islamic Education (LPIT) Ya Ummi Fatimah Pati. The sampling technique in this research used the census method, that is the entire population was sampled. Methods of collection by using questionnaires and obtained 106 respondents. Data analysis using Structural Equation Modeling (SEM) and analysis tool using AMOS program. The results of this study indicate that Service Leadership has a positive influence on Knowledge Sharing, Leadership Serving has a positive influence on Affective Commitment, Affective Commitment has a positive influence on Knowledge Sharing, Affective Commitment positively mediates the influence of Serving Leadership on Knowledge Sharing