Upon King Albert's death in 1439, Ulrich took up the cause of his widow Elizabeth of Luxembourg, and presided at the coronation of her infant son Ladislaus the Posthumous with the Holy Crown of Hungary in 1440.

In 1452, he forced Emperor Frederick III to hand over the boy king Ladislaus to his keeping, practically making him ruler of Hungary.

In 1454 his power was increased by his succession to his father's vast wealth; and after the death of John Hunyadi at the Siege of Belgrade in 1456, he was named Captain General of Hungary by Ladislaus,[3] an office previously held by his rival.

Ulrich's triumph did not last: On 8 November, he entered the fortress of Belgrade with King Ladislaus; the next day he was killed by agents of John Hunyadi's son László in unknown circumstances.

[5] Ulrich's estates were claimed by his widow Catherine, his son-in-law Matthias Corvinus - the younger brother of László Hunyadi - as well as Count John of Gorizia, and Emperor Frederick III of Austria, who outlived his rivals.

On his mother's side, Ulrich was the closest surviving male descendant of Francesco I da Carrara, lord of Padua.