This report compiles and shares some of the lessons learnt from implementing post-Fukushima actions related to human and organisational factors (HOF), including at nuclear facility operating companies, technical support organisations, research institutions, and regulatory authorities. It summarises a two-phase information-gathering exercise, overseen by the NEA Working Group on Human and Organisational Factors, about the requirements and guidelines that countries and nuclear licensees have adopted since the accident. The report discusses the central role of human and organisational performance in mitigating extreme external events and the management of severe accidents. It addresses the importance of validating the ability to perform these actions, and the challenges associated with performing such validations with fidelity to the conditions likely to be present during such events. The report concludes by providing four key recommendations that seek to promote greater sharing of information and the identification of best practices.