S. Ansky was born in Chashniki, Belarus, then part of the Russian Empire. Initially he wrote in Russian, but from 1904, he became known as a Yiddish author.

Under the influence of the Russian narodnik movement, Ansky became interested in ethnography. Between 1911 and the outbreak of the Great War in 1914 he headed ethnographical expeditions to various Jewish towns of Volhynia and Podolia.

He is best known for his play The Dybbuk or Between Two Worlds. The play was first staged in the Elyseum Theatre in Warsaw two months after the author's death in Otwock on November 8, 1920. Ansky was also the author of the song Di Shvue (The Oath), which became the anthem of the Jewish, Socialist Bund party. He was the author of the poem (later made into a song), In Zaltsikn Yam (In the Salty Sea), that was dedicated to the Bund as well.

Ansky's ethnological collections were locked away in Soviet vaults for years, but some material has come to light since the 1990s. The State Ethnographic Museum at St Petersburg holds a good deal of it.

Some of his vast collection of cylinder recordings made on these expeditions have been transferred to CD as well.

His ethnographic report of the deliberate destruction of Jewish communities by the Russian army in the First World War, The Enemy at His Pleasure: A Journey Through the Jewish Pale of Settlement During World War I, has become a major source in the historiography of the war's impact on civilian populations.

In 1917 he was elected to the Russian Constituent Assembly as a Social-Revolutionary deputy.