During normal and predictable circumstances, employees' occupational calling (i.e., a transcendent passion to use their talent and competencies toward positive societal impact and a sense of meaningfulness derived from working in a chosen occupational domain) is observed to be relatively stable. However, with the onset of the COVID-19 pandemic, circumstances have become anything but normal and predictable, thus putting employees' sense of occupational calling to the test. In this study, we investigate the possibility that occupational calling fluctuates across days during situations of crisis, and we identify antecedents and consequence of such fluctuations. To test our model, we conducted a daily diary study of 66 nurses working in intensive care units over 5 consecutive work days in a specialized Wuhan hospital that only admitted confirmed COVID-19 patients during the peak of the pandemic in China. We found that the daily number of code blue events (i.e., cardiopulmonary resuscitation efforts with the primary goal of patient revival) was positively related to daily occupational calling for nurses. Moreover, individual differences in prosocial motivation predicted the average level and variability of occupational calling over the 5 days, which subsequently related to the nurses' job performance. Our study sheds light on how occupational calling enables people with the needed occupational knowledge and skills to function effectively in crisis situations.