Mor began his career apprenticing to Jan van Scorel in Utrecht; by 1540 he was Van Scorel's assistant. After visiting Italy, Mor had joined Antwerp's Guild of Saint Luke by 1547. Two years later, he was painter to Emperor Charles V's minister. For twenty years Mor traveled among the Habsburg courts--Augsburg, Lisbon, London, Madrid, Rome--painting portraits that became a virtual hall of fame of the era's rulers.
Adding Netherlandish attention to detail, polished technique, and fidelity to likeness to the grandness of Titian's portraits, Mor's influential new style wedded formality with penetrating insight into character. He became King Philip II's painter in 1554, probably thanks to the success of his portrait of Philip's wife. However, Philip's support of the Inquisition, his increasing ruthlessness in promoting Roman Catholicism and his quashing of humanist thought prompted Mor's escape from Spain. He did, however, continue to work for Philip in Utrecht, Brussels, and Antwerp.