In this article, we quantify the effects of nurses on health care delivery and patient health in the context of an unintended and policy-induced nurse shortage. Our empirical strategy takes advantage of a parental-leave program in Denmark, which offered any parent the opportunity to take up to one year’s absence per child aged 0–8. Combining the policy variation with administrative employer–employee match data, we document substantial program take-up among nurses, who could not be replaced on net despite public education and immigration expansion efforts to mitigate the employment effects. We find that the parental leave program reduced hospital and nursing home nurse employment by 15% and 10%, respectively. Using detailed patient health records, we find detrimental effects on hospital-care delivery as indicated by a large increase in 30-day readmission rates among acute myocardial infarction patients. We find no evidence for an increase in hospital mortality. In nursing homes, we estimate a large increase in mortality.