He was the oldest son of Duke January I of Żagań by his wife Scholastika, daughter of Rudolf III, Duke of Saxe-Wittemberg and Elector of Saxony. After his father"s death in 1439, he inherited the Duchy of Żagań with his younger brothers Rudolf, Wenceslaus and January II the Mad.
Deposed during 1461–1468, he recovered the Duchy in this year until shortly before his death. He was named after his maternal great-grandfather, Balthasar, Landgrave of Thuringia (Scholastika"s maternal grandfather). In 1449 the Duchy was divided into two districts: Żagań and Przewóz.
Balthasar and Rudolf received Żagań as co-rulers while Przewóz was give to January II and Wenceslaus, also as co-rulers.
In 1450, together with Rudolf, Balthasar went on a pilgrimage to Rome. After his death, Balthasar went to Prussia (Polish region), fighting on the Teutonic side and trying to gain a Lieutenancy.
Without obtaining this position, he returned to Żagań in 1457. On his return, he found a complicated situation, as January II established himself as a Governor of the Duchy during his absence, and forced the Żagań states to paid homage to him.
In the following years Balthasar was involved in the Silesian political affairs, directly against George of Poděbrady, King of Bohemia.
Balthasar was forced to escape. During 1461-1467 Balthasar lived in exile in Wroclaw, where he led the urban army. After having unsuccessfully appealed to King George for the recovery of his domains, he went to Rome, where he obtained the support of Pope Pius World War II However, the expedition failed after Balthasar"s defeat by January II in KożuchóWest
During the war between Matthias Corvinus and George of Poděbrady, he was at the side of the Hungarian King.
In 1469 he paid homage as a vassal of Hungary. However, soon the Hungarian King began to support January II against him.
In 1472 January II invaded again Żagań and took control over the government. This happened on 15 July 1472.
He was buried in the Ducal mausoleum in the Augustinian church of Żagań.
