A marriage to Maximilian seemed more likely for Sophia, mostly because she and her sisters were all attractive brides for European nobility, since they all had claims to the thrones of Austria and Luxembourg through their mother Elisabeth.

It's unknown when exactly the negotiations for a marriage between Sophia and Prince Frederick of Brandeburg, son of Elector Albrecht III Achilles started.

There is a presumption that the idea could emerged in the summer of 1470, when Polish deputies Dziersław z Rytwian and Stanisław Ostroróg visited Brandenburg.

[3] In 1473 the Polish royal representatives Paweł Jasieński (starost of Chełm and Belz) and Stanisław Kurozwęcki led the negotiations for the marriage between Sophia and Frederick, which ended with the signing of the formal betrothal on 7 December of that year in the city of Cadolzburg.

As for the political motives of this marriage, Sophia's father Casimir IV sought allies among the Germans, since he was concerned with the influence of the Holy Roman Emperor Frederick III, who supported the rule of the Polish prince Vladislaus in Bohemia.

Originally the marriage contract was planned to be signed on 20 March 1474 and on 23 June 1474, during a meeting between representatives of both Brandenburg and Poland in Pniewy.

On 11 November 1475 Elector Albrecht III Achilles gave as a Bride price for his future daughter-in-law the amount of 64,000 florins.

She was accompanied, among others, by Andrzej Oporowski, Bishop of Przemyśl, voivodes Maciej z Bnina Moszyński and Mikołaj z Kutna, and by Piotr Kurozwęcki, Marshal of the Court.

By a letter wrote by her mother-in-law Anna of Saxony dated 13 April 1505 was known that Sophia was seriously ill. Four months later, on 30 August, her mother died.

After the death of Sophia, her husband arranged an extremely boisterous wake: 1,500 cups of wine were drunk and 2 oxen and 600 fish were eaten over the course of the night.