Since 2006, several cities and states have implemented paid sick leave mandates. We examine the effects of paid sick leave mandates in Washington, D.C. (2008) and Connecticut (2011) on leave-taking behavior. After these policies are implemented, there are significant decreases in the aggregate rate of illness-related leave taking, relative to control groups, for both those directly affected and those not directly affected by the policy. Our results suggest that such policies can provide large positive public health externalities by allowing sick workers to stay home rather than coming to work and spreading their illness to customers and coworkers.