The author deals with one of the most interesting and controversial persons who were on the Roman throne in the 4th century, Julian the Apostle. In the first part of the paper, there will be historical facts about his life and the environment that influenced Julian's religious belief. In the central part of the work we will deal with the motives that have led Emperor Julian to fully accept the pagan religion and how this transformation reflected on his relationship with the Church. In the end, we will try to give an answer to the question to what extent its reform was successful.