He co-founded the Center of Contemporary Jewish Documentation, established to collate documentation relating to the persecution of Jews during World War II. He also assisted Edgar Faure at the Nuremberg Trial. Poliakov went on to serve as director of research at the National Center for Scientific Research (CNRS) from 1954 until 1971.
According to historian Jos Sanchez, Poliakov was the first scholar to critically assess the disposition of Pope Pius XII toward various issues connected to the Holocaust. In November 1950, Poliakov wrote "The Vatican and the 'Jewish Question' - The Record of the Hitler Period-And After," in the influential Jewish journal Commentary. While this article was the first to consider the attitude of the papacy during World War II and the Holocaust, it was not until 1963, when German playwright Rolf Hochhuth published his play Der Stellvertreter that discussion of Poliakov's initial investigations in this area took on worldwide significance.
Although little noted at the time, Poliakov's 1951 Breviaire de la haine was the first major work on the genocide, predating Raul Hilberg's Destruction of the European Jews by a decade. It received some good reviews in opposition to the prevailing opinion in studies at the time that a major genocide of six million Jews was logistically impossible and thus could not have happened. Poliakov said in his Memoires that he refrained from even using the word genocide which was considered unfit for publication in 1951 when his groundbreaking work was first published.
- L'étoile jaune - La situation des Juifs en France sous l'Occupation - Les législations nazie et vichyssoise (Editions Grancher, October 1999 - three texts: a book of 1949, an article in Historia magazine in 1968 and a text of 1980) ISBN 2-7339-0642-9
- Poliakov, Léon (1 June 1951). Bréviaire de la haine: Le IIIe Reich et les Juifs [Harvest of Hate, the 3rd Reich and the Jews] (in French). Calmann-Lévy. ISBN 978-2-7021-5174-7. OCLC 897450164., translated 1956 as Harvest of Hate: The Nazi Program for the Destruction of Jews in Europe
- The History of Anti-Semitism: From the Time of Christ to the Court Jews (orig. 1955; this tr. 1966; repr. University of Pennsylvania Press, 2003) ISBN 0-8122-1863-9
- The History of Anti-Semitism: From Mohammed to the Marranos (orig. 1961; tr. 1973; repr. University of Pennsylvania Press, 2003) ISBN 0-8122-1864-7, ISBN 0-8122-3767-6
- The History of Anti-Semitism: From Voltaire to Wagner (orig. 1968; tr. 1975; repr. University of Pennsylvania Press, 2003) [preview at Google Books ISBN 0-8122-1865-5
- The History of Anti-Semitism: Suicidal Europe. 1870-1933 (orig. 1977; tr. 1984; repr. University of Pennsylvania Press, 2003) [preview at Google Books ISBN 0-8122-3769-2
- The Aryan Myth: A History of Racist and Nationalistic Ideas In Europe (Barnes & Noble Books (1996)) ISBN 0-7607-0034-6
- Jews Under the Italian Occupation (coauthored with Jacques Sabille) (Howard Fertig; 1st American ed edition (December, 1983)) ISBN 0-86527-344-8
- «Moscou, troisième Rome» Moscow, The third Rome
- «L`Auberge des musiciens» (memoir)
- «L`envers du Destin» (autobiography)
- "De l'antisionisme à l'antisémitisme" (1969)
- Léon Poliakov; Josef Wulf, eds. (1959). Das Dritte Reich und seine Denker — Dokumente (in German). Berlin-Grunewald: Arani.
- Kirkup, James (11 December 1997). "Obituary: Leon Poliakov". The Independent. Retrieved 5 May 2011.
- Arendt, Hannah (1952-03-01). "Breviaire de la Haine: Le IIIe Reich et les Juifs, by Léon Poliakov" [Harvest of Hate: The Third Reich and the Jews, by Léon Poliakov]. commentarymagazine.com. Calmann-Lévy. ISSN 0010-2601. OCLC 488561243. Archived from the original on 2012-01-15. Retrieved 2015-03-16.
Léon Poliakov’s excellent book on the Third Reich and the Jews is the first to describe the last phases of the Nazi regime on the basis, strictly, of primary source material. This consists chiefly of documents presented at the Nuremberg Trials and published in several volumes by the American government under the title Nazi Conspiracy and Aggression, These volumes contain, in addition to captured Nazi archives, a considerable number of sworn reports and affidavits by former Nazi officials. Mr. Poliakov, with a reasoned obstinacy, tells the story as the documents themselves unfold it, thus avoiding the prejudices and preconceived judgments that mar almost all the other published accounts.
- Poliakov, Léon (1981). L'Auberge des musiciens [Musicians Inn] (in French). Paris: Mazarine. p. 178. ISBN 9782863740729. OCLC 461714504. as cited in p247 of Bensoussan, Georges (2008). David Bankier; Dan Mikhman, eds. "Holocaust Historiography in Context: Emergence, Challenges, Polemics and Achievements". Berghahn Books. pp. 245–254. ISBN 9789653083264. Retrieved 2015-03-15.