Sigismund, the son of King Casimir IV Jagiellon and Elisabeth of Austria, had followed his brothers John I of Poland and Alexander I of Poland to the Polish throne.
Their elder brother Vladislaus II of Bohemia and Hungary had become king of Hungary and Bohemia.
Sigismund had been christened as the namesake of his mother's maternal grandfather, Holy Roman Emperor Sigismund, who had died in 1437.
After his father's death, Sigismund was the only son who did not hold any land titles.
In the years 1495-1496, he had addressed his older brother, the Lithuanian Grand Duke Alexander, and demanded the separation of a domain from the Lithuanian Duchy, but had been refused.
Queen Dowager Elisabeth Habsburg had also tried without success to ensure the succession of Sigismund to the throne of Austria.
Also, the disastrous and unsuccessful invasion of Bukovina led by his oldest brother King John I Albert had dispelled the plans for placing Sigismund on the Moldavian throne.
Eventually, Sigismund had come under the care of Vladislaus II, King of Bohemia and Hungary, from whom he had received the duchy of Glogów in 1499 and Opava in 1501, and in 1504 had become governor of Silesia and Lower Lusatia.
After the death, at forty-five, of King Alexander on August 19, 1506, Vasili III of Moscow, who had succeeded his father Ivan III in 1505, advances his bid for the Polish throne, but Polish nobles chose Sigismund.
Sigismund arrives in Vilnius, where he is elected by the Lithuanian Ducal Council on September 13, 1506, as Grand Duke of Lithuania, contrary to the Union of Mielnik, which involves a joint Polish-Lithuanian election of a monarch.