He was the third but second surviving son of Ernst II, Duke of Saxe-Gotha-Altenburg and Charlotte de Saxe-Meiningen.

After the death of his older brother August without sons (1822), Frederick (the only surviving male of the house) inherited the duchy of Saxe-Gotha-Altenburg.

Frederick fought - after military training - in the Napoleonic campaigns and was heavily wounded.

During these stays outside of his duchy, he left the government in hands of his secret advisor Bernhard August von Lindenau.

Altenburg was thereafter ruled by the Duke of Saxe-Hildburghausen, whose dukedom was transferred to Saxe-Meiningen along with Saxe-Saalfeld, which Saxe-Coburg gave up in return for receiving Saxe-Gotha.