Previous studies on working from home (WFH) and employee well-being have produced conflicting results. We hypothesize that giving workers a choice over whether to use WFH plays a crucial role in the consequences for well-being. This has a series of testable implications for empirical work. Using panel data from the UK, our fixed effects estimates show that not only the actual use, but also the pure availability of WFH is linked with improved job-related and overall mental health. Not controlling for the pure availability of WFH implies that the positive influence of the actual use of WFH is underestimated. However, we find a positive link between the use of WFH and overall mental health only for the years before and after the pandemic. The link was negative during the COVID-19 crisis where WFH was largely enforced. Moreover, gender moderates the influence of WFH on mental health. For women, both the actual use and the pure availability of WFH are positively associated job-related and overall mental health. For men, we find a more mixed pattern where either only the pure availability or only the actual use has an influence on mental health. Men are more likely to over- or underrate the consequences of WFH than women.