This paper investigates the effects of a mandatory, universal prescription drug insurance policy on health behaviors and outcomes within a public health care system providing physician and hospital services free of charge. Using Canadian longitudinal data, we show that the reform improved individuals' general health while reducing body mass index and smoking. However, the program also increased drinking and had no significant impact on mental health, physical activity, or preventive care. We also examine the mechanisms through which these effects can play a role, as well as the heterogeneous effects. Estimates suggest that the policy decreased SES‐based disparities in health.