Tekeli advanced further in his military career in Russia during the Seven Years' War, at the beginning of which he had the rank of second major. On 30th (old style - 19th) of August 1757, he was wounded during the Battle of Gross-Jägersdorf. After his participation in the storming of the Küstrin Fortress, he was raised to the rank of lieutenant colonel in 1758. Tekeli participated in the Battle of Zorndorf, the Battle of Kay and the decisive Battle of Kunersdorf in 1759, which marked Prussia's defeat in the war.