Sergei Shtemenko was born to a peasant family in the village of Uryupinsk. His original surname was Shtemenkov with the suffix "-ov" like other local people, but after the death of his father, his mother changed the surname to Ukrainian style: Shtemenko. Shtemenko volunteered for the Red Army at 1926. In 1930 he joined the All-Union Communist Party (b), and he graduated from the Anti-Aircraft School in Sevastopol at the same year. After several years in the Artillery, he moved to the Armored Corps, completing his studies in the Mechanization and Motorization Academy in 1937. He commanded a tank regiment until September 1938, when he was summoned to the General Staff Academy. In late August 1939, with other cadets, Shtemenko was assigned as a staff officer to the Soviet forces preparing for the Invasion of Poland, and took part in the operation. During the Soviet-Finnish War he served as an assistant in the General Staff. After matriculating from the Academy at autumn 1940, Shtemenko's request to be transferred to the new Tank Corps was rejected and he was posted as an aide to General Mikhail Sharokhin, a department chief in the Operations Directorate.