Economists traditionally describe individuals as well-informed and rational decision-makers. Recent developments in behavioural economics, which lies at the intersection between psychology and economics, challenge these assumptions and describe the common cognitive biases that affect us all. The resulting decision errors are particularly frequent in health and health care given the predominance of uncertainty and the complexity of choices. Interventions aiming at correcting, or exploiting, these biases to improve decisions of citizens, patients, and health professionals have recently emerged. We present here a critical synthesis of findings and discuss potential applications in our health system.