During the Seven Years' War, Lentulus served at the royal headquarters and was sent on several diplomatic missions; and after the Battle of Lobositz, he delivered the victory message to London. He then fought at the Battle of Prague and, subsequently, at the Battle of Kolin. He particularly distinguished himself at the Battle of Rossbach when he pursued the fleeing French army. Subsequently, Lentulus led a brigade formed by the "Garde du Corps" Cuirassier Regiment Nr. 13 and the "Gens d'Armes" Cuirassier Regiment Nr. 10. In the Battle of Leuthen, under command of Major General Hans Joachim von Zieten, he again distinguished himself in the attack on the Austrian left flank, and Frederick gave him a reward of a thousand thalers. In 1757, Lentulus was promoted to major general.