A Fukushima-like nuclear accident does not have to be caused by nature. Similar results could be wrought by a dedicated terrorist group that gained access to a nuclear power plant and disabled its safety systems. To guard against natural accidents, terrorist sabotage, and possible combinations of these two classes of events, nuclear plant operators and regulators should consider a combined approach called nuclear safety-security. Although safety and security programs have different requirements, they overlap in key areas and could support and enhance one another. Nuclear facilities could improve safety-security in technical ways, including more secure emergency electrical supplies, better security for control rooms, and, at new plants, reactor containment structures built to survive attacks by terrorist-flown airplanes. At the institutional level, regulators could strengthen the safety-security interface by requiring that it be built into the life cycle of nuclear plants, from design to dismantlement. The authors offer technical and institutional recommendations on how, for example, the International Atomic Energy Agency can support improved safety-security at nuclear plants globally by creating design standards that relate to both accidents and threats while encouraging countries to accept International Physical Protection Advisory Service missions that review security and physical protection systems and provide advice on best practices.