Lew Sapieha was born on April 4, 1557, in the village Astroŭna, near Vitebsk (now in the Beshankovichy district of Vitsebsk Region), at that time Grand Duchy of Lithuania, to a family of magnates, whose influential connections and rich estates enabled the talented young man to start a brilliant career.
Lew Sapieha was a son of Ivan Ivanavich Sapieha (died 1580), the Starosta (major) of Daragichyn and Voivode (general, head of the region) in Padlyassie (which is currently the region of Poland). His mother was countess Bagdana Drucka-Sakalinskaya (died 1584). He had two brothers: Grygor (served as Padkamory (secretary) in Orsha, died in1600) and Andrej (Starosta in Orsha, then Kashtalyan (treasurer) in Vitsebsk and Voivode in Mscislau; died in 1611). He had also 3 sisters.