In the nuclear industry, thirty years of extensive international cooperation have led to the establishment of the nuclear safety culture concept. By describing the main steps of the development of this concept, the purpose of this paper is to share several lessons learned. Three areas for improvement are proposed: firstly, further work is needed to reach a common understanding of organisational culture and safety culture; secondly, international cooperation is to be fostered to devise appropriate assessment methodologies in order to evaluate and enhance safety culture and finally, the role of national safety authorities should be clearly stated and further described