Leckie was born in Philadelphia, Pennsylvania on December 18, 1920 to an Irish Catholic family of eight children. He grew up in Rutherford, New Jersey. He began his professional writing career, before World War II, at age 16 as a sports writer for The Bergen Evening Record in Hackensack, New Jersey.
In 1941, the day after the attack on Pearl Harbor, Leckie enlisted in the United States Marine Corps. He served in combat in the Pacific theater, as a scout and a machine gunner in the 1st Marine Division. He participated in every major 1st Marine Division campaign except Okinawa. Robert Leckie was wounded by blast concussion on Peleliu and evacuated, ending his combat tour.
Following World War II, Leckie worked as a reporter for the Associated Press, the Buffalo Courier-Express, the New York Journal American, the New York Daily News and The Star-Ledger. He married Vera Keller, a childhood neighbor, and they had three children: David, Geoff and Joan. According to Vera, in 1951 he was inspired to write a memoir after seeing South Pacific on Broadway and walking out halfway through. He said ‘I have to tell the story of how it really was. I have to let people know the war wasn’t a musical.’ His first and best-selling book, Helmet for My Pillow, a personal war memoir, was published in 1957. Leckie subsequently wrote more than 40 books on American war history, spanning from the French and Indian War (1754—1763) to Desert Storm (1991). Robert Leckie died in 2001 after fighting a long battle with Alzheimer's Disease.
Leckie's war memoirs, Helmet for My Pillow, along with Eugene B. Sledge's book With the Old Breed, formed the basis for the 2010 HBO series The Pacific, the successor to Band of Brothers. He was portrayed in the miniseries by James Badge Dale.