In the same year, Pope Alexander VI named him governor of Perugia.

[2] On 17 February 1502 he was one of six cardinals and six prelates who accompanied the pope on his trip to Piombino.

[1] Pope Alexander VI made Castellar a cardinal priest in the consistory of 31 May 1503.

He received the titular church of Santa Maria in Trastevere on 12 June 1503.

[1] On 7 July 1504 he left Rome to visit Ferdinand II of Aragon.