 This study examined the relationship between psychological capital, organizational commitment and organizational citizenship behavior among nurses during the COVID-19 pandemic. The results showed that nurses' psychological capital, organizational commitment and organizational citizenship behavior were all at an upper middle level. Additionally, organizational commitment partially mediated between psychological capital and organizational citizenship behavior. This suggests that nurses' psychological capital has a positive effect on their organizational citizenship behavior through the mediating role of organizational commitment. Thus, it is important for nursing administrators to prioritize the mental health and organizational behavior of nurses during the COVID-19 crisis.