He was the son of Duke Ernest Ferdinand of Brunswick-Bevern (1682–1746) and his wife, Eleanor Charlotte of Courland.
Under the guidance of his uncle Louis Ernest, he commanded the Both'sche regiment during the War of the Austrian Succession.
After the outbreak of the Seven Years' War, he travelled to Dresden at the end of 1756, where King Frederick II of Prussia gave him command of the Saxon infantry regiment Prince Xaver.
In 1781, his elder brother August William died and Frederick Charles Ferdinand inherited Brunswick-Bevern and became provost of St. Blaise and the St. Cyriacus Abbey in Brunswick.
However, with permission of the King of Denmark, who promoted him to field marshal in 1782, he took up residence in Glücksburg Castle.