The objective of the study was to examine the impact of HRM practices on organizational performance (OP) with an analysis of the mediating effect of organizational citizenship behavior (OCB) in Nepalese public financial institutions. A quantitative research approach and a casual comparative research design have been used in the study. The sample size has been 480 respondents, out of which 472 usable respondents have been received. Structural equation modeling (SEM) has been used to analyze the direct and mediating effects. The study’ findings revealed that HRM practices had a positive and significant impact on organizational performance. OCB partially mediated the relationship between HRM practices and organizational performance in Nepalese public financial institutions. OCB is a prominent factor in Nepalese public financial institutions that strengthens the link between HRM practices and organizational performance.