Crichton was born in Albuquerque, New Mexico, and grew up in Bronxville, New York. He served in the infantry during World War II, and was wounded during the Battle of the Bulge in 1944. Before returning to the States, he ran an ice cream factory on the outskirts of Paris; it was, he said, his decompression chamber. He attended Harvard University on the GI Bill and was a member of the famed class of 1950. His father, Kyle Crichton, was a writer/editor at Collier's magazine and author of novels and biographies, including a biography of the Marx Brothers. He also wrote a column for The New Masses, a Marxist weekly, under the name Robert Forsythe.

Crichton's first book, The Great Impostor, published in 1959, was the true, if picaresque, story of Fred Demara, an impostor who successfully assumed scores of guises including serving as a Trappist monk, a Texas prison warden and a practicing surgeon in the Canadian Royal Navy. The book was a bestseller and adapted into a successful 1961 film with Tony Curtis in the starring role. Crichton's second book, The Rascal and the Road, was a memoir about his escapades with Demara.

The non-fiction books were "hack-work", he said, written to support a growing family. In 1966, he published his first novel, The Secret of Santa Vittoria. The New York Times critic Orville Prescott wrote: "If I had my way the publication of Robert Crichton's brilliant novel...would be celebrated with fanfares of trumpets, with the display of banners and with festivals in the streets." The book was on the New York Times bestseller list for over 50 weeks, spending 18 of them at the top of the list, and became an international bestseller. Set in an Italian hill-town and telling the story of local resistance to the Nazis during World War II, the novel was adapted into a Golden Globe winning film of the same name in 1969.

Crichton's second and last novel, The Camerons, published by Knopf in 1972, was drawn from the lives of his great grandparents, a Scottish coal mining family. It too was a bestseller. He had intended to write a sequel, but the work was never completed.

Among countless magazine articles, he was best known for an essay "Air War--Vietnam," published by The New York Review of Books, in 1967. The essay was distributed all over the world.

Crichton died in 1993 in New Rochelle, New York, at the age of 68.

Crichton was married to Judy Crichton, the first woman documentary producer at CBS Reports, CBS's documentary unit, and the founding executive producer of the PBS historical documentary series, The American Experience. They had four children: Sarah Crichton, publisher and writer; Rob Crichton, lawyer; Jennifer Crichton, teacher and writer. Susan Crichton is deceased.

A brother, Andrew S. Crichton, was a senior editor at Sports Illustrated from its founding in 1954 until 1976. A nephew, Kyle Crichton, is an editor on the Foreign Desk of The New York Times.