Born on 10 November 1418, he was the son of Duke Bernard I of Brunswick-Lüneburg and his wife, Margaret of Saxony.

After the death of his father, Bernard, Frederick assumed joint rule of the Principality of Lüneburg alongside his brother Otto.

Their reign was marked by significant developments, including the extensive expansion of Celle Castle and the implementation of reforms aimed at improving the legal rights of farmers in relation to their landlords.

In 1452, he established a monastery dedicated to the Holy Cross (Heylig Kreuz) and invited Franciscan friars to settle in Celle.

However, following the death of his second son, Otto V, in 1471, Frederick left the monastery to assume control once more, acting as regent for his three-year-old grandson, Henry.