In Japan around 100,000 working carers leave their jobs each year. While long-term care leave was legislated in 1995 with the aim of ensuring that working carers do not leave their jobs, few workers use such leave. The Japanese government has addressed this problem in 2016 by proposing amendments to the Child Care and Family Care Leave Act to allow workers to take care leave more flexibly. Focusing on another aspect of combining work and care, this paper addresses the possibility that workers who remain in their jobs may suffer from the effects of having to combine work with providing care. Although fatigue among carers has been raised as a problem in the context of issues that arise outside the workplace, such as abuse or murder of care receivers or suicide among carers, the effects that fatigue may have on carers’ work is rarely a topic of discussion. The results of our original data analysis show that physical fatigue due to providing care while working full time raises the risk of having an accident while at work and failing to meet work quotas. It is therefore crucial to consider means of ensuring that working carers who come to the office as usual are able to maintain their health and work performance.