Lenni Brenner was born into an Orthodox Jewish family. He became an atheist at 10, and a left political activist at 15. His involvement with the Black civil rights movement began on his first day in the organized left, when he met James Farmer of the Congress of Racial Equality, later the organizer of the "freedom rides" of the early 60s. He was active in the mid 50s with Bayard Rustin, later the organizer of Martin Luther King's 1963 "I had a dream" March on Washington.
He was arrested three times during civil rights sit-ins in the San Francisco Bay Area. He spent thirty-nine months in prison when a court revoked his probation for marijuana possession, because of his activities during the 1964 Berkeley Free Speech Movement at the University of California. Immediately on imprisonment, he spent four days in intense discussion with Huey Newton, later the founder of the Black Panther Party, who he encountered in the court holding tank. Subsequently, upon his release in 1968, he worked with Kathy Cleaver and other Panthers.
Brenner was an antiwar 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. He worked with Kwame Ture (AKA Stokely Carmichael), the legendary "Black Power" leader of the Student Nonviolent Coordinating Committee, in the Committee against Zionism and Racism, from 1985 until Ture's death in 1998.
Brenner is the author of four books: Zionism in the Age of the Dictators, The Iron Wall: Zionist Revisionism from Jabotinsky to Shamir, Jews in America Today, and The Lesser Evil: A study of the Democratic Party. In 2002 he edited 51 Documents: Zionist Collaboration with the Nazis, which contains complete translations of many of the documents quoted in Zionism in the Age of the Dictators and The Iron Wall. In 2004 he edited Jefferson & Madison On Separation of Church and State: Writings on Religion and Secularism. In 2013, Brenner co-authored Black Liberation and Palestine Solidarity with Matthew Quest. His books have been favorably reviewed in eleven languages by prominent publications, including the London Times, The London Review of Books, Moscow's Izvestia and the Jerusalem Post.
Brenner has written over one hundred articles for many publications, including New York's Amsterdam News, the Anderson Valley Advertiser, The Atlanta Constitution, CounterPunch, The Jewish Guardian, The Nation, The Washington Report on Middle East Affairs, Middle East Policy, Middle East International, The Journal of Palestine Studies, The New Statesman of London, Al-Fajr in Jerusalem, and Dublin's United Irishman.