During the Austro-Turkish War, Kienmayer excelled in a skirmish against a force of Turks that attacked the Austrian outposts in April 1788. Later that year, he served under Prince Josias of Saxe-Coburg-Saalfeld in the siege of Khotyn Fortress and was promoted major in November. He fought in the Battle of Focșani on 21 July 1789 and received promotion to Oberst-Leutnant in recognition of a successful raid carried out afterward. After the Battle of Rymnik in September, Coburg sent Kienmayer to carry the victory dispatch to Emperor Joseph II. He quickly returned to the front and executed another successful cavalry raid in November, capturing a senior Turkish officer. Promoted to Oberst (colonel), he assumed command of the "Levenehr" Dragoon Regiment # 19. He was also awarded the Military Order of Maria Theresa, Austria's highest honor for valor, on 21 December 1789 for bravery in the face of the enemy.