McCarry served in the United States Army, where he was a correspondent for Stars and Stripes, was a small-town newspaperman, and was a speechwriter in the Eisenhower administration. From 1958 to 1967 he worked for the CIA, under deep cover in Europe, Asia, and Africa. However, his cover was not as a writer or journalist.

McCarry was editor-at-large for National Geographic and contributed pieces to The New York Times, The Wall Street Journal, The Washington Post, and other national publications.

McCarry was best known for a series of books concerning the life of super spy Paul Christopher. Born in Germany before WWII to a German mother and an American father, Christopher joins the CIA after the war and becomes one of its most effective spies. After launching an unauthorized investigation of the Kennedy assassination, Christopher becomes a pariah to the agency and a hunted man. Eventually, he spends ten years in a Chinese prison before being released and embarking on a solution to the mystery that has haunted him his entire life: the fate of his mother, who disappeared at the beginning of WWII. The books are notable for their historical detail and depiction of spycraft, as well as their careful and extensive examination of Christopher's relationship with his family, friends, wives, and lovers.