The COVID-19 pandemic and the policy measures to control its spread—lockdowns, physical distancing, and social isolation—have coincided with the deterioration of people’s mental well-being. We use data from the UK Household Longitudinal Study (UKHLS) to document how this phenomenon is related to the situation of working parents who now have to manage competing time demands across the two life domains of work and home. We show that the deterioration of mental health is worse for working parents, and that it is strongly related to increased financial insecurity and time spent on childcare and home schooling. This burden is not shared equally between men and women, and between richer and poorer households. These inequalities ought to be taken into account when crafting policy responses.