Frederick was the eldest son of Duke Magnus II of Brunswick-Lüneburg, Prince of Wolfenbüttel, and his consort Catherine of Anhalt-Bernburg.

A minor upon his father's death in 1373, he was not declared to have reached the age of majority until 1381, while Duke Otto of Brunswick-Göttingen acted as his guardian.

Like his father, he was thrust into the Lüneburg Succession War, which he and his brothers attempted to end in 1373 by a treaty with the Ascanian dukes of Saxe-Wittenberg.

In May 1400, Frederick took part in an assembly of the Princes of the Holy Roman Empire in Frankfurt; the purpose of the meeting was to discuss the deposition of the incapable king Wenceslaus.

By order of King Rupert, the murderers had to donate an altar in Saint Peter's Church, Fritzlar to atone for their crime.