This master's thesis analyses the safety of nuclear-powered ships in a comprehensive way. 60 accidents over a 34-year period have been analysed and, based on this data only 1.76% of maritime accidents are reported. A descriptive analysis of these known accidents, their causes and consequences was performed. The thesis also briefly describes the impact on the marine environment as well as the role that the human error plays in causing a maritime nuclear accident and human casualties as a result of radiation. The master's thesis gives examples of occasional entry of nuclear-powered ships into Croatian territorial waters as part of pre-arranged military visits and describes the procedure for accepting such a ship. The aim of the paper is to get acquainted with the safety of nuclear-powered ships based on publicly available information and to highlight possible improvements. It emphasises the importance of educating all participants in the process of adopting nuclear-powered ships, a high level of training, training, preparation and coordination of operational forces and emergency services. This paper uses scientific research methods of analysis, synthesis, comparisons, general system theory with search of relevant internet sources.