Yegorov (sometimes spelled Egorov) was born into a peasant family near Samara in central Russia. He joined the army of the Russian Empire in 1901 and qualified as an officer in 1905. During World War I he rose to the rank of Lt-Colonel and was wounded five times. In 1904 he had joined the Socialist Revolutionary Party, but after the Bolsheviks took power he accepted the new regime and became a commander in the Red Army.

During the Russian Civil War Yegorov was commander of the Red Army's Southern Front and played an important party in defeating the White forces in Ukraine. In 1920 Yegorov was one of the Red Army commanders during the Polish-Soviet War. In this campaign he was a close colleague of Stalin and of Semyon Budyonny.

In 1925-26 Yegorov was sent as a military adviser in China. In 1927 he was the Red Army commander in Belarus. In 1931 was appointed Deputy People's Commisar for Defence and Chief of the General Staff of the Red Army. In 1934 he became a candidate member of the Central Committee of the Communist Party.

In 1935 he was one of the first five Marshals of the Soviet Union when this rank was created.

Because of his old connections to Stalin and Budyonny, Yegorov seemed to be safe from the wave of arrests that swept through the Red Army in 1937 as Stalin's purge gathered pace. He was officially listed as one of the judges at Tukhachevsky's trial in June 1937, although it is doubtful that any such trial took place. But he was himself arrested in February 1938, and executed some time later - the date in February 1939 was later officially quoted, but some Soviet sources gave his death as late as 1941. The rationale to his liquidation is quite nebulous. He was rehabilitated by Nikita Khrushchev after Stalin's death.