In this thesis entitled: "Analysis of railway transport and accidents in the Republic of Croatia from 2015 to 2020", railway transport and accidents were investigated. The research is directed in accordance with the goal of this thesis. The goal itself refers to gaining insight into determining the causes and circumstances of railway accidents and incidents. The possibility of increasing the safety of railway traffic as a system was also considered. Different applicable scientific research methods were used in the work. They included the following: analysis, synthesis and comparison. A partial application of the forensic approach to research, respecting a systematic approach, can also be cited. Certain results were achieved with the above approach. Studying the railway systems in operation in selected countries, it can be argued that their development is at different technical and technological levels. Of course, as in other modes of transport, accidents also happen in railway transport. Therefore, a common feature of railway systems of various countries can be observed. This feature can be determined by trying to achieve satisfactory reliability of the entire system. The first railway in Croatia was opened in 1860. and developed according to possibilities. Investments in railway infrastructure have increased with the accession of the Republic of Croatia to the European Union. It is in the interest of every country, including the Republic of Croatia, that its railway transport system performs its function in the best possible way. The state tries to influence the reduction of accidents. Therefore, in the observed time period, the undertaken research was started. The role of the Accident Investigation Agency must be emphasized here, which uses strictly defined procedures. The AIN reports on investigations and analyzes of types of accidents and incidents identified the causes and circumstances of their occurrence. The efforts of the Republic of Croatia in the improvement of rail traffic have recently been somewhat consistent. As a recommendation for improvement, the effort to provide continuous support to all involved state bodies and other interested entities in order to improve all segments of railway transport in the Republic of Croatia can be considered.