Königsegg-Erps was born in Vienna, the firstborn son of Imperial Chamberlain Count Albert zu Königsegg-Rothenfels and Countess Maria von Manderscheid-Blankenheim.
Count Karl Ferdinand was the elder brother of Maximilian Friedrich von Königsegg-Rothenfels, Elector and Archbishop of Cologne.
His uncle, Count Dominik von Königsegg-Rothenfels, then Imperial Ambassador to Paris, brought him into the diplomacy as his secretary.
In 1742 he became Obersthofmeister at the court of governor Maria Anna of Austria and finally, as Minister Plenipotentiary, the highest administrator of the Austrian Netherlands between 1743 and 1744.
After the death of Archduchess Maria Anna, he returned to Vienna to become Obersthofmeister at the court of Empress Dowager Elisabeth Christine.