He was educated locally and later entered the College of St Antony at Louvain, which had just been founded for Irish Roman Catholic students, and received the Franciscan habit on 1 November 1607.
After his ordination to the priesthood, Hickey was appointed lecturer in theology at Leuven, and subsequently professor in the college of St Francis at Cologne.
In 1619 he was summoned to Rome to collaborate with Father Luke Wadding in preparing the Annals of the Franciscan Order for publication, and the works of Duns Scotus.
He took an active part in the labours of the commissions appointed by Pope Urban VIII to revise the Roman Breviary, and to examine into the affairs of the Eastern Church.
During the discussions which were held in Rome concerning the doctrine of the Immaculate Conception, Hickey won distinction by his learning and acuteness.