In 1920-1930s the West Ukrainian areas, Galicia and Volhynia, incorporated into the independent Poland (the Second Rzeczpospolita) according to the 1921 Riga peace treaty, became the centre of the Ukrainian national movement. However the political activity of the Ukrainian nationalists was strongly limited by the Polish government. One of the few organizations of the Ukrainian people, capable to maintain social activity, was the Church. In Galicia the Ukrainian Greek Catholic Church traditionally supported the Ukrainian national movement. By contrast, in Volhynia, where the Ukrainians belonged to the Orthodox Church in Poland, the population was generally apolitical and showed no interest in the Ukrainian nationalism. This paper explores the dynamic of growing Ukrainization efforts within the Church, starting with individual initiatives of using the Ukrainian language in worship and ending up with appearance of bishops who promoted the idea of Ukraine’s political and ecclesiastical independence.