The main purpose of this research is to examine to what extent the affective commitment as mediating variable can influence the person organization fit towards employee performance in an institution. This research used quantitative causalities method. The data were collected through questionnaires with Likert scale and the sampling technique in this research was nonprobability sampling. In the testing of structure model and data analysis, the researcher uses variance-based SEM that was PLS which included other model namely convergent validity, discriminant validity, and composite reliability as well as inner model which include path coefficient. The research shows that there is significant positive influence of person organization fit with the affective commitment, as P-value was 0,000 (smaller than 0,05) and T-statistic >1,96. Moreover, affective commitment which had significant positive influence toward employee performance was shown as P-value was 0,032 (smaller than 0,05) and T-statistic >1,96. In this research, furthermore, affective commitment was proven to mediate person organisation fit towards employee performance. This was shown from the score of effect coefficient –direct influence is as smaller as 0,762 than the indirect influence.