Throughout his life, Jan Harmensz. Muller made drawings, engravings, and paintings. He also worked at his family's successful publishing business, The Gilded Compasses. His father, a printmaker and art dealer, first trained him. Hendrick Goltzius's Mannerist figure style also profoundly influenced Muller. Whether he actually apprenticed to Goltzius in Haarlem or learned by copying Goltzius's prints and drawings is unknown. Muller had contact with many artists practicing in Prague, which was a flourishing cultural center. This contact probably occurred as the result of Muller's ties to the Dutch sculptor Adriaen de Vries, who was working at Emperor Rudolf II's court there. De Vries and Muller were related by marriage. Though he made engravings based on his own designs, most seem to have been after works by Haarlem Mannerists such as Goltzius or by Prague artists, including de Vries and Hans von Aachen. Muller spent 1594 through 1602 in Naples and Rome, making engravings. Upon returning to Amsterdam, he abandoned this work and began managing his father's publishing business, which he had inherited. He managed The Gilded Compasses for the remainder of his life. Muller's will and inventories show that he also painted, though only one painting is firmly attributed to him today.