Purpose This study aims to examine the influence of organizational citizenship behavior’s sub-constructs including altruism, civic virtue, sportsmanship, conscientiousness and courtesy on knowledge sharing behavior (KSB). It also pays attention to the effects of group emotional climate on the relationship between organizational citizenship behavior and knowledge sharing. Design/methodology/approach This research was conducted based on the quantitative research strategy by applying structural equation modeling. Using a random sampling method, this research surveyed 116 participants and analyzed the data via partial least equation modeling. Findings The results claim that altruism, conscientiousness and civic virtue have a significant effect on KSB, while the relationship between courtesy and sportsmanship with KSB were not significant. Furthermore, the findings depict that positive and negative workgroup emotional climate would impede or enhance KSB among people with a high level of altruism, conscientiousness and civic virtue. Practical implications Given the importance of knowledge sharing in the today knowledge economy, by comprehending the influence of group organizational citizenship behavior’s sub-constructs on knowledge sharing, managers would improve organizational knowledge sharing by developing a culture encouraging altruism, conscientiousness and civic virtue as a substitute for incentive pay. Moreover, promoting an emotionally supportive climate fosters knowledge sharing within people. Originality/value This study makes three distinct additions to the knowledge sharing literature. First, although there are little studies that investigate the relationship between organizational citizenship behaviors (OCB) and KS, a few of them examine the effects of OCB’s sub-constructs on KS behavior. Second, this is one of the first studies that examined the moderating role of workgroup emotional climate regarding knowledge sharing. Finally, examining the effect of OCB’s sub-constructs on KS in an Iranian public sector would contribute to the literature by broadening the examination of the constructs in a different context.