Dumas was born in Sweet Home, Arkansas, in 1934 and lived there until the age of ten, when he moved to New York City; however, he always kept with him the religious and folk traditions of his hometown. In Harlem, he attended public school and graduated from Commerce High School in 1953. After graduating, he enrolled in the Air Force and was stationed at Lackland Air Force Base in San Antonio, Texas, where he met future wife, Loretta Ponton. The couple married in 1955 and had two sons, David in 1958 and Michael in 1962. Dumas was in the military until 1957, at which time he enrolled at Rutgers University but never attained a degree. In 1967 Dumas began work at Southern Illinois University as a teacher, counselor, and director of its "Experiment in Higher Education" program. It was here that he met fellow teacher and poet Eugene Redmond, forming a close collaborative relationship that would prove so integral to Dumas's posthumous career.
During his life, Dumas was active in civil rights and humanitarian efforts, including transporting food and clothing to protesters in Mississippi and Tennessee. While serving in the military, he spent eighteen months at Dhahran Air Force Base in Saudi Arabia, where he developed an interest in the language, culture, religion, and mythology of the Arab world.
On May 23, 1968, at approximately 12:15 a.m., Dumas was shot to death at the age of 33 by a New York City Transit Police officer on the southbound platform of the 125th Street Station of the New York City Subway's IRT Lenox Avenue Line. The circumstances of the shooting are somewhat murky, particularly since the Transit Police Department's records of the shooting were destroyed when the agency merged into the New York City Police Department in 1995. According to an Associated Press report shortly after the shooting, the officer claimed that Dumas had been threatening another man with a knife. The officer said that he ordered Dumas to drop the knife, but that Dumas instead turned, attacked the officer, and slashed the officer's cheek. The officer stated that he fired three times.
Multiple accounts over the years have said that Dumas was killed by the officer in a case of "mistaken identity," but it is unclear what the source of that characterization is.
Dumas was buried in Long Island National Cemetery in Suffolk County, New York.
His death is mentioned in the poem "An Alphabet of My Dead," by Poet Laureate Robert Pinsky, as well as the poem "Night, for Henry Dumas" by Aracelis Girmay.
Dumas's first collection of short stories was Ark of Bones and Other Stories, published in 1974, posthumously edited by his friend, poet Eugene Redmond, who also edited other volumes of his work, including his poetry collection, Play Ebony, Play Ivory (1974). Subsequent books include an unfinished novel, Jonah and the Green Stone (1976), Rope of Wind and Other Stories (1979), Goodbye, Sweetwater: New and Selected Stories (1988) and Knees of a Natural Man: The Selected Poetry of Henry Dumas.
His short story "Will the Circle Be Unbroken?" was included in the 2004 Dark Matter: Reading The Bones anthology edited by Sheree Thomas.
Dumas was influenced by jazz, studying with Sun Ra during the mid-1960s, and in turn influenced jazz musicians. For example, his poem "Black Paladins" became the title track for a recording by Joseph Jarman and Famoudou Don Moye.
Dumas claimed some of his earliest influences to be Moms Mabley and gospel music. His experiences as a black child growing up in the south during the 1930s and '40s were frequent themes in his writings. His time spent on the Arabian Peninsula influenced him as well, and he eventually drew not only on black Christianity and Islam, but on Sufi mysticism, Hinduism, Buddhism, and Native American and African myths and religions. In the 1960s Dumas became increasingly involved with both the Black Power Movement and the Black Arts Movement, immersing himself in music: gospel, spirituals, jazz, and blues. Writer Margaret Walker and musicians James Brown and John Coltrane proved to be major influences on his writing at this time.
Both his fiction and his poetry developed themes of the Black Aesthetic movement, in addition to themes of nature and the natural world.