Giovanni Sforza had been the first husband of Lucrezia Borgia, but their marriage was annulled in 1497 by her father, Pope Alexander VI, on the grounds of supposed non-consummation and the alleged impotence of the groom.
However, Pope Julius II decided to retain control over Pesaro, and he did not allow Galeazzo Sforza to be invested with the title.
Pope Julius II then gave the title to his nephew, Francesco Maria I della Rovere, Duke of Urbino.
Galeazzo Sforza married Ginevra , daughter of Ercole Bentivoglio and Barbara Torelli, on 4 August 1507, but had no children.
On 12 March 1515, while returning from Parma to Milan together with Duke Massimiliano Sforza, he was hit by a shot from an arquebus rifle.