After the war, Coonts served as a flight instructor for A-6 aircraft for two years, then did a tour as an assistant catapult and arresting gear officer aboard USS Nimitz (CVN-68). After being honorably discharged from active duty as a lieutenant in 1977, Coonts pursued a Juris Doctor (J.D.) degree at the University of Colorado, graduating in 1979. He then worked as a lawyer for several oil and gas companies, pursuing his writing interests in his free time. He retired from the Naval Reserve after 21 years of service as a Commander.
Coonts began writing Flight of the Intruder in 1984, and it was published by the US Naval Institute Press in 1986. That book, based in part on his experiences as an A-6 pilot during the Vietnam War, spent 28 weeks on the New York Times bestseller lists, and later (1991) was made into a movie. This launched his career as a novelist, and he continued writing adventure-thrillers, most of them based on the main character from his first book, Jake Grafton. Coonts has also written several other series and stand-alone novels, but is best known for the Grafton books. In 1992, he was inducted into the Academy of Distinguished Alumni at his alma mater, West Virginia University. In 2014 West Virginia University awarded him an honorary Doctor of Letters degree.
Today Coonts continues to write, having had sixteen New York Times bestsellers (out of 36 books). He lives in Colorado with his third wife, Deborah Jean. He is divorced from romantic mystery novelist Deborah Coonts.