He published two early books of verse in England, before moving to Sydney, Australia in 1954, where at twenty-three he was already a prominent book and film critic. He became literary editor of The Bulletin, the country's leading weekly, in 1964, and published three more collections of verse.
Higham was then chosen by the University of California as Regents Professor, an honor accorded to leading literary figures in foreign countries, and while at UC Santa Cruz he made the discovery of the lost footage of It's All True, Orson Welles' uncompleted Latin American triptych. In The Films of Orson Welles (1970) he alleged that the film maker suffered from a "fear of completion" which led to Welles abandoning projects when they were nearly finished in order to be able to blame others for their flaws. Friends of Welles, in particular Peter Bogdanovich, criticised this thesis. The book earned Higham a full-page spread in Newsweek as the film detective, and he was engaged as New York Times Hollywood feature writer for the Sunday Theatre Section.
His first best seller was Kate (1975), the first authorised biography of Katharine Hepburn, and was followed by others: Bette, the Life of Bette Davis, Lucille Ball, The Duchess of Windsor (1988, 2004) and Howard Hughes, the latter a basis of Martin Scorsese's movie The Aviator. Higham's Trading with the Enemy: The Nazi American Money Plot 1933-1949 detailed U.S. industry's links with Nazi Germany. He also wrote Sisters: The Story of Olivia De Havilland and Joan Fontaine, in 1984, about the legendary feud between Olivia de Havilland and Joan Fontaine.
Higham has also written Murder in Hollywood: Solving a Silent Screen Mystery on the death of William Desmond Taylor and a biography of Jennie Churchill (Dark Lady: Winston Churchill's Mother and Her World 2006).
In 1980, Higham published a controversial biography, Errol Flynn: The Untold Story in which he alleged that Errol Flynn was a bisexual fascist sympathiser who spied for the Nazis before and during World War II and had affairs with Tyrone Power, Howard Hughes, and Truman Capote.
Tony Thomas, in Errol Flynn: The Spy Who Never Was (Citadel, 1990) and Buster Wiles in My Days With Errol Flynn: The Autobiography of a Stuntman (Roundtable, 1988) have denounced Higham's claims as fabrications. According to Thomas and Wiles, Flynn was notorious in Hollywood as a womaniser and was a left wing supporter of the Spanish Republic in the Spanish Civil War and of the Cuban Revolution, even narrating a documentary titled the Cuban Story shortly before his death.
Higham lives in Los Angeles.