Forrest was born into a middle-class family in Chicago. His mother was Catholic and from New Orleans, while his father's family was Baptist. His paternal great-grandmother had a role in his early upbringing. Forrest later attended a racially integrated high school after winning an award, but he was a generally mediocre student except for writing. His parents divorced in 1956; his mother remarried, and the couple opened a liquor store.
Forrest attended Wendell Phillips grade school and Hyde Park High School. He then attended Wilson Junior College for a year, and then took classes at Roosevelt University and the University of Chicago before dropping out, leaving to serve as a Public Information Officer in the military. After leaving the service, he returned to the University of Chicago and worked for the Catholic Interracial Council's Speakers Bureau. In 1969, he began working for Muhammad Speaks, a Nation of Islam newspaper. Forrest would become the last non-Muslim editor of the paper.
His first novel, There is a Tree More Ancient than Eden, was published in 1973, and included an introduction from Ralph Ellison. Nobel Prize Laureate Toni Morrison served as publisher's editor for There is a Tree More Ancient than Eden, and his next two novels The Bloodworth Orphans, and Two Wings to Veil My Face. These three novels were known as the Forest County Trilogy. He cited Charlie Parker, Dylan Thomas, William Faulkner, Eugene O'Neill, Ralph Ellison, and his parents' religions as inspiration.
He joined the creative writing and literature staff of Northwestern University in 1973, and from 1985 to 1994, he headed their African-American Studies department. His last novel, Divine Days, was modeled on Ulysses by James Joyce. A novel over 1,100 pages long, Divine Days was called "the War and Peace of African-American literature" by noted scholar and Harvard professor Henry Louis Gates.
He died of cancer in Evanston, Illinois at age 60. Meteor in the Madhouse, a series of connected novellas was published posthumously in 2001, his widow Marianne Forrest serving as literary executor.
- There is a Tree More Ancient than Eden (Random House, 1973)
- The Bloodworth Orphans (Random House, 1977)
- Two Wings to Veil My Face (Asphodel, 1984)
- Relocations of the Spirit: Collected Essays (Asphodel, 1994)
- Divine Days (Another Chicago Press, 1992)
- Meteor in the Madhouse (Northwestern University, 2001)
- Cawelti, John G. Leon Forrest: Introductions and Interpretations. Bowling Green State University Popular Press, 1997, p. 3.
- Cawelti, John G. Leon Forrest: Introductions and Interpretations, 1997, pp. 4-5.
- Cawelti, John G. Leon Forrest: Introductions and Interpretations, 1997, p. 4.
- Onishi, Norimitsu. "Leon Forrest, 60, a Novelist Who Explored Black History", The New York Times, November 10, 1997.
- Northwestern University
- Byerman, Keith. "Angularity: An Interview with Leon Forrest - Interview". African-American Review, Fall 1999.
- Undercover Black Man