Pieter van Laer was possibly a pupil of Esaias van de Velde in Haarlem. His early work shows the influence of this painter as is evidenced by a drawing signed Pieter Bodink (formerly in the collection of A. Welcker), which is close to van de Velde's style. He traveled to Rome in 1625 via France, likely in the company of his brother Roeland. In 1626 their father is also recorded in Rome as a witness to a will. Here he became a member of the Bentvueghels, an association of mostly Flemish and Dutch artists in Rome who were known for their initiation rituals, which involved a lot of drinking. Pieter van Laer's nickname in Italy was "Il Bamboccio", which means "ugly doll" or "puppet". This was an allusion to van Laer's ungainly appearance, as he is said to have had unusually long legs, short chest and almost no neck. Pieter van Laer was also known for his pointed moustache. Van Laer shared a home in the Via Margutta with Giovanni di Filippo del Campo, whose pupil he is said to have been according to certain art historians. However, such apprenticeship is unlikely since the two artists had approximately the same age. He was also a close friend of Joachim von Sandrart in Rome.