Francia’s portrait of the young Federico II Gonzaga (1500–1540) has been famous since 1903, when Herbert Cook recognized that it was the subject of one of the most suggestive series of letters written about a Renaissance portrait. These outlined Isabella d’Este’s determination to commission a portrait of her son to ease her loneliness while he was a hostage at the papal court of Julius II and her anger when the completed portrait was confiscated. Further letters showed that Isabella swiftly lost interest in the portrait, giving it as a gift to a collector, while at the same time she and her husband, Francesco Gonzaga, commissioned a portrait of Federico from Raphael. In this paper, I examine this epistolary evidence to follow the shifting functions of a single portrait – from private keepsake to diplomatic conversation piece and gift – as well as the critical transition in collecting that followed it, as the Gonzaga set their sights on Raphael.