Verdonck was born in Turnhout. From his earliest years, he was in the household of Cornelis Pruenen, senator and treasurer of Antwerp; in addition he was a choirboy at Antwerp Cathedral until about the age of 9. In 1572 he went to Spain to be part of the choir of Philip II in Madrid, where he stayed until his voice broke in early 1580, at which time he returned to the Netherlands to study in Antwerp with Séverin Cornet, and possibly with Hubert Waelrant as well. His earliest works, published along with those of Cornet, date from this period.