The aim of the study was to investigate whether organizational justice, job satisfaction and affective commitment are the important determinants of organizational citizenship behavior (OCB) in KP Police and to check whether the relationship of organizational justice and OCB is mediated in serial by job satisfaction and affective commitment. Multi stage cluster sampling technique which is a type of probability sampling was employed and eight police stations were finally selected and considered as clusters. Questionnaires were distributed among all the available 386 policemen working in these eight police stations. 300 dully filled questionnaires were received making an active response rate of 78%. SPSS and PROCESS softwares were used data. The results of the study confirm previous findings that organizational justice, job satisfaction and affective commitment are related to OCB however, the relationship between organizational justice and OCB is partially mediated by job satisfaction and affective commitment in serial.The study found KP Policemen highly dissatisfied with the extrinsic factors such as duty hours, and working conditions, etc. In order to promote OCB among KP Policemen, concrete steps shall be taken to improve working conditions and justice perceptions among KP Police.