This article analyses the life and deeds of Saint Visarion Saraj and the historical results of his deeds. This saint was of Serbian descent, but remained relatively unknown in the Serbian-speaking world until today. Therefore, this article aims to bring Saint Visarion Saraj closer to the Serbian reading public. Visarion played the most important role in preventing the spread of the Church Union and Catholicism in Transylvania at the end of the 17th and beginning of the 18th century. In addition to the life and deeds of the saint, this article analyses the social and religious situation in Transylvania at that time, as well as the process of deciding the Church Union between the local Orthodox Church and the Roman Church. This process was presented to the readers at the beginning of the article, and then the actions and working methods of Saint Visarion Saraj against the Union were analysed and discussed. At the end of the article, the canonization of Visarion Saraj and the reception of his deeds and personality in the modern world were also briefly presented.