Beinart was born in Cambridge, Massachusetts, United States, in 1971. His parents were Jewish immigrants from South Africa (his maternal grandfather was from Russia and his maternal grandmother, who was Sephardic, was from Egypt). His father's parents were from Lithuania. His mother, Doreen (née Pienaar), is former director of the Harvard's Human Rights film series at the John F. Kennedy School of Government, and his father, Julian Beinart, is a former professor of architecture at the Massachusetts Institute of Technology. His stepfather is theatre critic and playwright Robert Brustein. Beinart attended Buckingham Browne and Nichols School in Cambridge. He then studied history and political science at Yale University, where he was a member of the Yale Political Union, and graduated in 1993. He was a Rhodes Scholar at University College, Oxford University, where he earned an M.Phil. in international relations in 1995.
Beinart worked at The New Republic as the managing editor from 1995 to 1997, then as senior editor till 1999, and as the magazine's editor from 1999 to 2006. For much of the time, he also wrote The New Republic's signature "TRB" column, which was reprinted in the New York Post and other newspapers. From 2007 till 2009 he was a Senior Fellow at the Council on Foreign Relations. Beinart is Associate Professor of Journalism and Political Science at the City University of New York and a Schwartz Senior Fellow at New America. Beinart has written for Time, The New York Times, The New York Review of Books, and some other periodicals. Occasionally Beinart has appeared on various TV news discussion programs. His achievements at a very young age have earned him the accolade "wunderkind". In March 2012, he launched a new blog, "Open Zion", at Newsweek/The Daily Beast. He was also a senior political writer for The Daily Beast.
In 2012, he was named by Foreign Policy magazine on its list of 100 top global thinkers.
Israeli liberal newspaper Haaretz announced on November 4, 2013, that Beinart would be hired as a columnist beginning January 1, 2014. The same day, the Atlantic Media Company said Beinart would join National Journal and write for The Atlantic's website beginning in January. Beinart would cease operating his blog at The Daily Beast.
Beinart is the author of the book The Good Fight: Why Liberals—and Only Liberals—Can Win the War on Terror and Make America Great Again, published in 2006. Drawing upon the work of the mid-century American theologian Reinhold Niebuhr, Beinart argues that, paradoxically, the only way for America to distinguish itself from the predatory imperial powers of the past is to acknowledge its own capacity for evil.
Beinart was a vocal supporter of the 2003 U.S.-led invasion of Iraq, but by 2006 as he published his first book, he "had concluded that it had been a tragic mistake", according to George Packer in The New Yorker. His second book, The Icarus Syndrome: A History of American Hubris, published in 2010, in Packer's words, "look[ed] back at the past hundred years of U.S. foreign policy in the baleful light of recent events [and found] the ground littered with ... the remnants of large ideas and unearned confidence [as demonstrable in] a study of three needless wars", the World War I, Vietnam War, and the Iraq War.
In his 2010 essay "The Failure of the American Jewish Establishment" in the New York Review of Books, Beinart has argued that the tensions between liberalism and Zionism in the U.S. may tear the two historically linked concepts apart. He argued that by abetting Israel's occupation of the Palestinian territories, American Jewish leaders risk alienating generations of younger American Jews who find the occupation to be morally wrong and incompatible with their liberal politics.
He expanded on this argument for his 2012 book, The Crisis of Zionism.
He has warned that greater military engagement against ISIS could be detrimental to America.
Since 2003, Beinart is married to Diana Robin Hartstein, a lawyer. They live with their two children in New York City. He keeps kosher, regularly attends an Orthodox synagogue and sends his children to a Jewish school.The Crisis of Zionism. New York, NY: Times Books. 2012. ISBN 978-0-8050-9412-1.
The Icarus Syndrome: A History of American Hubris. New York, NY: HarperCollins. 2010. ISBN 978-0-06-145646-6.
Peter Beinart (June 10, 2010). "The Failure of the American Jewish Establishment". The New York Review of Books.
The Good Fight: Why Liberals—and Only Liberals—Can Win the War on Terror. New York, NY: HarperCollins. 2006. ISBN 978-0-06-084161-4.