Guy Walters, was born in Kensington, London. A descendant of Richard Harris Barham, he was educated at Cheam School, Eton College and Westfield College, University of London (now part of Queen Mary, University of London).

After working at The Times from 1992 to 2000, he became a novelist. His first book, The Traitor, was published in 2002, and concerns the British Free Corps, a British unit of the Waffen-SS. The Leader (2003) is set in a Britain ruled by Oswald Mosley as a Fascist dictator. The Occupation (2004) takes place during the German Occupation of the Channel Islands. The Colditz Legacy (2005) is set in Colditz Castle during the war and the 1970s. With James Owen, he edited The Voice of War in 2004, a collection of Second World War memoirs. In 2006 he published Berlin Games, a history of the 1936 Berlin Olympics, which was shortlisted for the 2006 William Hill Sports Book of the Year and the 2007 Outstanding Book of the Year by the North American Society for the Sociology of Sport. His most recent book is Hunting Evil (2009), a history of how the Nazi war criminals escaped after the war, and how they were brought to justice. He writes a blog for the Daily Telegraph website on historical subjects.

In October 2007, as part of his research for Hunting Evil, Walters visited the alleged Nazi war criminal Erna Wallisch at her flat in Vienna, Austria. Wallisch, a former concentration camp guard at Ravensbrück and Majdanek, was the seventh most wanted person on the Simon Wiesenthal Center's list of suspected war criminals from the Second World War. Although Wallisch refused to talk to Walters, the news of his encounter was widely reported.

In March 2008, Walters wrote an article for the Daily Mail comparing the 2008 Beijing Olympics to the 1936 Berlin Olympics: "Those who believe that Beijing 2008 will improve China's shameful human rights record," he wrote, "are surely as myopic to the realities of modern China as the appeasers of the 1930s were towards Hitler."

In April 2010, Walters accepted an offer to study for a PhD in history at Newcastle University.

He lives in Wiltshire with his wife Annabel Venning and two children. His brother, Dominic Walters, is the picture editor of Country Life magazine.