The present research investigated the relationship between workload, fatigue, and sleep quality of physicians and nurses in psychiatric hospitals by conducting a cross-sectional survey and a diary study. Both studies were conducted in China in early 2021, investigating the effect of workload on fatigue and sleep quality among psychiatric staff in a real-life setting. Study 1 was a cross-sessional survey, investigating 334 responses from physicians and nurses in five psychiatric hospitals, and Study 2 was a diary study examining the association between workload, fatigue and sleep quality in the working week of 48 psychiatric staff. The findings from the first study showed that the staff reported a high workload, and fatigue and poor sleep quality were very prevalent. Workload was the strongest predictor of fatigue. In the diary study, workload and fatigue increased over the week, and sleep quality declined. This research has identified the importance of studying workload and its effects on psychiatric staff.