The Fukushima Daiichi nuclear power plant (NPP) accident that occurred on 11 March 2011 following a massive earthquake and tsunami was one of the most severe accidents ever experienced at a nuclear power plant and will have to be dealt with for many years by those in charge of nuclear safety (operators, safety bodies). Following the accident, nuclear regulatory authorities, governments and international organisations around the world took immediate actions to support Japan in its response. Under the control of nuclear regulatory authorities, operators begans undertaking a series of analyses and follow-up measures to ensure the safety of all nuclear facilities. This report outlines the actions taken by the OECD Nuclear Energy Agency (NEA) and its member countries. Key messages and their implications for ensuring high levels of nuclear safety are also summarised.