The aim of this article is to trace the influence of the polemical works of the Jesuit priest Piotr Skarga (1536–1612) on the religious life of Ukraine and on the Ukrainian culture of his era. The writings of Piotr Skarga, Stanislaw Orzechowski, Benedict Herbest, Herasym Smotrytsky, Ivan Vyshensky, and Hypatius Potius are the sources examined in the author’s scholarly study. Works about Skarga and his era by Józef Tretiak, Ludowik Piechnik, Janusz Tazbir, and Stanisław Cieślak, writings about interfaith polemics concern- ing the Union of Brest by Volodymyr Antonovych, Nikolaj Skabalanovich, Stepan Golubev, Vladimir Zavitnevich, Ivan Franko, Mykhailo Hrushevskyi, Kyrylo Studynskyi, Porfyriy Yaremenko, Ihor Mytsko, Borys Gudziak, Vitalii Shevchenko, Leonid Tymoshenko, and Ruslan Tkachuk, as well as courses in the history of Ukrainian literature are analyzed to comprehensively present Skarga’s impact on Ukrainian culture. A comparative methodol- ogy is applied. Skarga’s writing talent was brought out during his stay in Vilnius – one of the centers of Reformation movements in the Polish- Lithuanian Commonwealth, the residence of Kyiv Orthodox Metropolitans (1416–1795). The multi-confessionalism of Vilnius challenged Skarga. He wrote O jedności Kościoła Bożego (1577) – a book in which he expounds Tridentine ecclesiology, enumerating from his point of view heresies and schisms characteristic of the Orthodox East. He outlines the prospects of returning the Church of Kyiv to unity with the Apostolic See of Rome. In 1596 the Synod of Brest proclaimed union with the Catholic Church. Skarga was present at the synod as an observer and adviser. He pub- lished a documentary description of the synod’s proceedings – the book Synod Brzeski with an appendix – Obrona Synodu Brzeskiego (1597), which defends the canonical validity of the synod, adding a historical retrospec- tive to justify the need to overcome schism. These works became important catalysts in the development of the Ukrainian Greek Catholic Church, which proved its viability during the period of persecution and entered the post-communist era as a most creative spiritual force, combining the careful nurturing of local church tradition with the universality of the apostolic mission.