Efficiency and productivity, which enable the organization to achieve its objectives, play an important role in the continuation of organizational activities. The human factor has particular importance among the inputs of organizations and constitutes the greatest competitiveness of them. It has been observed that psychological capital, organizational citizenship behavior and person-organization fit, which contribute to the successful survival of organizations under increasing competition conditions with today's globalizing world economy, have led to positive results and behaviors in different sectors and with different variables. This research has been carried out to determine the effect of psychological capital on organizational citizenship behavior and the role of person-organization fit between these two variables. The sample of the study consisted of 575 participants working in the public sector in Ankara. The questionnaire was distributed to public servants in person and sent via e-mail and an online survey system. The collected data is analysed by frequency, reliability, correlation, confirmative factor analyzes and also structural equation modelling. The findings indicate that psychological capital is positively correlated with personorganization fit and organizational citizenship behaviour. Besides, the mediating role of person-organization fit was supported in the relationship between psychological capital and organizational citizenship behaviour, which is the main hypothesis of the study. It has been thought that the research will contribute to the studies and will give insight to both researchers and practitioners about psychological capital, organizational citizenship behavior and person-organization fit of public personnel.thought that the research results will provide insight into future studies and allow comparisons to be made.