His adherence to the Roman Catholic faith has been a matter of dispute. Evidence in his music suggests that he may have had Protestant sympathies, and indeed may have been an Anabaptist, although legal documents show him to have been a Catholic. It was a turbulent time of religious conflict—one of the reasons many local composers went to Italy and other countries—and Waelrant may have been deliberately unclear as to his beliefs; Antwerp changed hands several times during his life, alternately captured by Calvinists and the Catholic Habsburgs, and both sides suffered persecution. Some of Waelrant's simple psalm settings in the vernacular language suggest that he was a Protestant, and there is evidence that they were confiscated by Catholic church authorities at Kortrijk.