Brenner was born into an Orthodox Jewish family. He developed an interest in history from reading Hendrik Willem van Loon's The Story of Mankind which his brother had received as a bar mitzvah present. He became an atheist at age 10 or 12 and a Marxist at age 15. Brenner's involvement with the Civil Rights Movement began when he met James Farmer of the Congress of Racial Equality, later the organizer of the Freedom Rides of the early 1960s. He also worked with Bayard Rustin, later the organizer of Martin Luther King's 1963 "I Have a Dream" march on Washington.
Brenner was arrested three times during civil rights sit-ins in the San Francisco Bay Area. He spent 39 months in jail when a court revoked his probation for marijuana possession, because of his activities during the Berkeley Free Speech Movement at the University of California in 1964.
He was an anti-war activist from the first days of the Vietnam War, speaking frequently at rallies in the Bay Area. In 1963 he organized the Committee for Narcotic Reform in Berkeley. In 1968 he co-founded the National Association for Irish Justice, the American affiliate of the Northern Ireland Civil Rights Association.
In the 1990s, he and Kwame Ture (aka Stokely Carmichael), the legendary "Black Power" leader of the Student Nonviolent Coordinating Committee, co-founded the Committee against Zionism and Racism. They also published The Anti-War Activist.
In 2003, Brenner spoke at the inaugural meeting of Jews Against Zionism with his colleagues Alice Coy, Haim Bresheeth and Roland Rance who presented Brenner's book, 51 Documents: Zionist Collaboration with the Nazis.
Brenner spoke at an Israeli Apartheid Week event in 2011 at Berlin, Connecticut. According to the Anti-Defamation League, at an event called "One State Solution" at the Islamic Association of Greater Hartford, Brenner said that Jews were the largest donors to American political parties and that the Political system is as "crooked as a dog's hind leg". He also asserted that President Truman recognised Israel because of contributions from Jews.
His books have been widely translated, and have been reviewed in 11 languages, to mixed reviews. His books have received very positive reviews from the London Times, the London Review of Books, Booklist magazine, the Washington Report on Middle East Affairs, among many other publications. His articles have also appeared in a range of left wing and Middle East specialist journals, but have also gained attention on the far-right, such as the Institute for Historical Review. Brenner has opposed his work being used by those on the far-right, and those engaged in Holocaust denial.
Brenner has authored, co-authored and edited a number of books:
- Zionism in the Age of the Dictators – which argued that many Zionist leaders collaborated with fascism, particularly Nazi Germany in order to build up the Jewish presence in Palestine. First printed in 1983.
- The Iron Wall: Zionist Revisionism from Jabotinsky to Shamir, first published in 1984 by Zed Books, London.
- Jews in America Today
- The Lesser Evil – a study of the United States Democratic Party
- Black Liberation and Palestine Solidarity – a collection of selected essays that "discusses the historical response of African American freedom movements to the colonial settler state of Israel and its role in American Imperialism in the Middle East."
- Jefferson & Madison On Separation of Church and State: Writings on Religion and Secularism
- 51 Documents: Zionist Collaboration with the Nazis – translations of many of the documents quoted in Zionism in the Age of the Dictators and The Iron Wall
- Dan Falcone, Lenni Brenner: An Interview on Palestine Solidarity, Black Liberation and Anti-Zionism,' Truthout 18 October 2014.
- "It's All Rabbis and No Jews": An Interview with Lenni Brenner Palestine Solidarity Review 2004
- "Lenni Brenner (biographical details)". student.cs.ucc.ie.
- "Zionism Against Jews". inminds.co.uk.
- "Israeli Apartheid Week: A Year-by-Year Report" (PDF). Anti-Defamation League. 2012. Retrieved 29 April 2016.
- "Ecrasez l'Infame -- Authors -- Reviews of Lenni Brenner's books". stopmebeforeivoteagain.org.
- These include The Nation, Amsterdam News, Jewish Guardian, Atlanta Constitution, Washington Report on Middle East Affairs, Middle East Policy, Middle East International, Journal of Palestine Studies, New Statesman, Al-Fajr and United Irishman.
- Weber, Mark (July–August 1993). "Zionism and the Third Reich". Institute for Historical Review. 13 (4): 29–37. Retrieved 2 May 2016.
- Brenner, Lenni (9 April 2001). "Subject: [AL-AWDA] Lenni Brenner re holocaust deniers and other falsifiers". Institute for Historical Review. Retrieved 4 May 2016.
- Review of the book by Brenner in CounterPunch. First printed in 1983, reprinted in 2014. It has been translated into Japanese: Fuashizumu jidai no shionizumu, by Shiba Kensuke (芝健介), Hosei Daigaku 2001, German (in a revised edition), as Zionismus und Faschismus : über die unheimliche Zusammenarbeit von Zionisten und Faschisten, tr. Verena Gajewski Homilius, Kai, Berlin 2007, and Spanish as Sionismo y Fascismo, by Luis César Bou, Bósforo Libros, Madrid,2010,
- Mortimer, Edward (November 2, 1984). "Contradiction, collusion and controvers". The Times (London).
- Brenner, Lenni. "Lenni Brenner: The Iron Wall - Zionist Revisionism (1984)". www.marxists.de.
- Lenni Brenner and Matthew Quest, Black Liberation and Palestine Solidarity. (Atlanta: On Our Own Authority! Publishing, 2013).
- Lenni Brenner, 51 Documents: Zionist Collaboration with the Nazis, December 23, 2002 in CounterPunch, also (2002) Barricade Books - This book has been translated to Spanish by Luis César Bou as 51 Documentos Sobre la Colaboración Sionista con los Nazis Editorial Canaán, Buenos Aires, 2012.
<Dan Falcone, Lenni Brenner: An Interview on Palestine Solidarity, Black Liberation and Anti-Zionism,' Truthout 18 October 2014./>
- Lenni Brenner. Beyond the UN's Rhetoric: Holocaust History, CounterPunch, January 29, 2005.
- Lenni Brenner. The plot to stigmatize "51 Documents" on Amazon.com, CounterPunch, May 25, 2005.
- "It's All Rabbis and No Jews": An Interview with Lenni Brenner
- Interview with Lenni Brenner by JK Fowler for The Mantle March 19, 2011