The author studies the <i>Portrait of Jean Bossaert</i>, a painting that was stolen from the Poznan Museum in 1949 and reappeared on the art market in 1983. The attribution to the Master of Princely Portraits, a late 15th-century painter working in Brussels, is based on a comparative analysis of the style and technique of this panel and the two basic works given to the Master by Friedlander. X-ray examinations in particular reveal a similar painting technique. The study of the coat of arms on the back of the portrait allowed Ch. Van der Bergen-Pantens to identify the figure.