This article considers the reaction o f the Polish episcopate to the election of Felix V at the Council o f Basle in 1439. The schism caused by that election lasted until 1449. Since Władysław, King of Poland and Hungary was away, the Polish bishops decided not to back any of the parties that split the unity of the Catholic Church. Bishops who sympathized more or less openly with the Counsel o f Basle and its anti-Pope were brought into line in the following years. Eventually, on 7 July 1447 they all had to sign a pledge of allegiance to Eugenius’s successor, Nicholas V, as demanded by Poland’s new king Kazimierz Jagiellończyk. Although he had sympathized with the Council of Basle when in Lithuania, soon after ascending the Polish throne he decided to throw all his weight behind pope Nicholas V. By reviewing Polish reactions to the divisions and strife occasioned by the Council of Basle, the article argues that conciliarism, which had already struck deep roots at the Cracow University, exerted considerable influence on the Polish episcopate in mid-15th century.