Background and Objectives: Occupational stress is one of the most common psychiatric disorders in nurses during the COVID-19 pandemic. The present study aims to investigate the occupational stress level of nurses and its related factors during the COVID-19 pandemic. Methods: This is a systematic review study that was conducted in 2022 by searching for articles in both Persian and English in Web of Science, SID, Scopus, Google Scholar, Cochran, MagIran, IranDoc and PubMed databases without time limit. The used keywords were nurse, Iran, COVID-19, occupational stress, and job stress in Persian and English. Initial search yielded 3860 articles. Of these, 15 articles were finally reviewed. Results: In the reviewed studies, nurses’ occupational stress during the COVID-19 pandemic was at a high level. The highest score was related to the “demands” dimension and the lowest score was related to “the changes” dimension of the health and safety executive questionnaire. Demographic, occupational, and mental factors and quitting job had a significant positive relationship with nurses’ occupational stress, while low rest, job-related affective well-being, organizational commitment, productivity, organizational climate, and knowledge had a significant negative relationship with their occupational stress. Conclusion: The occupational stress of nurses is high during the COVID-19 pandemic. Occupational stress is related to demographic, occupational, psychological, and organizational factors. It is recommended to form committees to monitor nurses’ occupational stress in hospitals.