His time in Rome from 1532 to 1536 defined his artistic direction. He spent his days sketching ancient ruins and the ongoing construction of St. Peter’s Basilica. These drawings are now accurate records for architectural historians. Heemskerck became a leading figure of the Romanist movement in the Habsburg Netherlands. He combined Northern precision with Italian Mannerist forms. His work often features muscular figures and complex compositions. He was also a prolific designer of engravings, producing over six hundred designs that influenced later Dutch masters.

His portraits often find favour with modern collectors because of their psychological observation and his ability to capture candid moments. His paintings feel like modern snapshots rather than formal commissions. Works such as Jonah Cast Out by the Whale or his various hovering angels show a mastery of movement and light. His prints offer a window into the sixteenth-century imagination. They possess a clarity and directness that suits contemporary interiors. His art is a bridge between the medieval tradition and the dawn of the Baroque period.