The son of Sigmund Khevenhüller and nephew of the Carinthian governor ("Landeshauptmann") Christoph von Khevenhüller (1503–1557), young George became a councillor at the court of the Habsburg emperor Ferdinand I and his successor Maximilian II. In 1565 he was appointed governor of Carinthia, later also President of the Inner Austrian Court Chamber at Graz and Court Chamberlain of Archduke Charles II of Austria. He distinguished himself as an officer in the Ottoman–Habsburg wars in the Kingdom of Croatia. On 21 August 1578, Khevenhiller and Ban Krsto Ungnad went from Slunj to Bihać.