In 1631, Boym joined the Jesuits in Kraków, and was ordained a priest. In 1643, after almost a decade of intensive studies in the monasteries of Kraków, Kalisz, Jarosław and Sandomierz, Boym embarked on a voyage to Eastern Asia. He first traveled to Rome, where he obtained a blessing for his mission from Pope Urban VIII, and then proceeded to Lisbon. Later that year he embarked with a group of nine other priests and clerics on a voyage to Portuguese Goa, and then Macau. Initially he taught at St. Paul Jesuit College (Macau). He then moved to the island of Hainan, where he opened a small Catholic mission. After the island had been conquered by the Manchus, Boym had to flee to Tonkin in 1647.