Eckert was born in Buffalo, New York and raised in the Chicago, Illinois area, but has been a long-time resident of Bellefontaine, Ohio, near where he attended university. As a young man, he hitch-hiked around the United States, living off the land and learning about wildlife. He began writing about nature and American history at the age of thirteen, eventually becoming an author of numerous distinguished books for children and adults. Seven of his books have been nominated for the Pulitzer Prize in literature. One of his novels tells how the Great Auk went extinct.

In addition to his highly popular novels he has also written several screenplays and more than 225 "Mutual of Omaha's Wild Kingdom" television shows for which he received an Emmy Award.

In a 1999 poll conducted by the Ohioana Library Association, jointly with Toni Morrison, Allan W. Eckert was voted "Favorite Ohio Writer of All Time."

Eckert is the playwright of the outdoor drama entitled Tecumseh! which, in 1997, celebrated its 25th year of production at the multi-million-dollar Sugarloaf Mountain Amphitheater near Chillicothe, Ohio. His book on Blue Jacket was dramatized for outdoor performances and opened in 1982 outside of Xenia, Ohio. The production was eventually closed due to financial difficulties, but not before it was reported to have put over nine million dollars yearly into the local economy of southwest Ohio.

Eckert's Pulitzer Prize-nominated book A Time of Terror: The Great Dayton Flood was adapted for the stage as 1913: The Great Dayton Flood by W. Stuart McDowell and Timothy Nevits in 1996 and performed at the Wright State University Department of Theatre, Dance and Motion Pictures, featuring recorded narration by Martin Sheen, Ossie Davis and Ruby Dee. The production won a number of awards from the American College Theatre Festival XXIX at the Riffe Center, Columbus, Ohio, and subsequently opened the 1997 festival in the Kennedy Center, returning to Dayton that fall, where it played in the Victoria Theatre in Dayton.

Eckert has sparked controversy with his "hidden dialogue" technique in his historical narratives, using a novelist's technique to enhance dramatic events. After many years of research on a topic, he has felt free to recreate historical conversations and thoughts in what some critics have considered to be "an entertaining blend of fact and fiction" purporting to be a straight biography. His colorful evocations of history have been praised as more accessible than drier, more strictly factual, accounts. However, what he has termed “narrative biography” has been criticized as “an apparent euphemism for poetic license” . A Sorrow in Our Heart: The Life of Tecumseh in particular has been faulted as “A biography that succeeds better as fiction” which “in its interpretative zeal strays from the historical record to the point of being suspect”.