The study examined the effect of person-organization fit and organizational citizenship behavior of academic staff working in southwest Nigerian Public Universities. The study adopted a cross-sectional survey research design method. A sample size of 400 employees of the selected universities in South-West Nigeria was chosen from a total population of 8,540 employees. The stratified random sampling technique was adopted for the study. The Work Engagement Scale (WES), Organizational Citizenship Behaviour Checklist (OCBC), Personal Values Scale (PVS), and Value Congruence Scale were used to collect data (VCS). The statistical techniques used for data analysis were descriptive statistics, correlation, and regression analysis. All analysis was done using the statistical package for social science (SPSS) software version 25. Findings showed that value congruence (Coef. = 0.1770, P = 0.010), personality congruence (Coef. = 0.3400, P = 0.000), and work engagement congruence (Coef. = 0.1630, P = 0.001), have significant and positive effects on organizational citizenship behavior. Findings showed that 25.8% of the change in organizational citizenship behaviour was brought about by the dimensions of person-organization fit. The study concluded that person-organization fit has a significant positive effect on the organizational citizenship behaviour of academic staff working in South-Western Public Universities. The study recommended amongst others that qualified individuals with strong organizational fit and moral character are to be chosen for placement in the academic staff cadre structure of universities. The study established that value congruence, personality congruence, and work engagement congruence contribute significantly to organizational citizenship behavior of academic staff in the south-west Nigerian Public Universities.