Allen was born in Pittsburgh, Pennsylvania on December 8, 1889 to William Hervey Allen and Helen Ebey Myers. He graduated from Shady Side Academy in 1909, attended the United States Naval Academy from 1910 to 1911, and graduated from the University of Pittsburgh in 1915, where he also became a member of the Sigma Chi Fraternity.
He was a Midshipman with the United States Navy from 1909-1910.
He served as a 2nd Lieutenant in the 18th Pennsylvania Infantry on the Mexican border in 1916 during the Pancho Villa Expedition.
He served as a Lieutenant in the 28th (keystone) Division, United States Army during World War I and fought in the Aisne-Marne offensive July–August 1918. He was wounded in action in August 1918.
He wrote Toward the Flame (1926), a nonfictional account of his experiences in the war.
His first book, Wampum and Old Gold, was awarded the Yale Younger Poets Prize.
Allen is best known for his work Anthony Adverse. He also planned a series of novels about colonial America called The Disinherited. He completed three works in the series: The Forest and the Fort (1943), Bedford Village (1944), and Toward the Morning (1948). The novels tell the story of Salathiel Albine, a frontiersman kidnapped as a boy by Shawnee Indians in the 1750s. All three works were collected and published as the City in the Dawn. Allen also wrote Israfel (1926), a biography of American writer Edgar Allan Poe.
For a period of time, Allen taught at the Porter Military Academy in Charleston, South Carolina. He also taught English at Charleston High School which at that time, although public, was only for boys. (The girls went to Memminger.) There he met and befriended DuBose Heyward.
From 1926 to 1927, he was on the faculty at Vassar University.
In the 1940s, he co-edited the Rivers of America Series with Carl Carmer. Allen was a good friend of Marjory Stoneman Douglas and instigated her writing The Everglades: River of Grass. Allen was close friends with Robert Frost and Ogden Nash.
He married Ann Andrews on June 30, 1927. They had three children: Marcia, Mary Ann and Richard.
Allen died at his home, called the Glades, in Coconut Grove, Florida, aged 60, from a heart attack, and was found by his wife.Wampum and old gold. Yale University Press. 1921.
Toward the Flame, George H. Doran Company, 1926 reprint. University of Nebraska Press. 2003. ISBN 978-0-8032-5947-8.
Israfel: The Life and Times of Edgar Allan Poe (1926) reissued 1934.
Anthony Adverse (1933) ISBN 4-87187-890-2
Action at Aquila, Farrar & Rinehart, (1938)
The Forest and the Fort (1943)
Bedford Village (1944)
Toward the Morning (1948)
The City in the Dawn (1950)
Achmed Abdullah, Hervey Allen, ed. (2003). Lute and Scimitar. Kessinger Publishing. ISBN 978-0-7661-7626-3. (reprint)