Huynh earned his degree in chemistry from Saigon University in 1962. After the outbreak of the Vietnam War, Huynh was drafted into the South Vietnamese army, where he reached the rank of first lieutenant, and received a gold and a silver medal. Huynh was shot and paralyzed during the war, resulting in his trip to the United States in 1963 for physical therapy.
Huynh decided to stay in the United States, and earned an M.A. in Comparative Literature in 1971 from Long Island University, and in 1973 he earned an M.A. in French from the University of Missouri in Columbia, Missouri.
His writing career began when his book The Land I Lost was published in 1982. The book received the ALA Notable Children's Book award, the ALA Booklist Editors' Choice award, the Notable Children's Trade Book in the Field of Social Studies, the Library of Congress Children's Books award, the William Allen White Children's Book Award, the Friends of American Writers Award, and the Blue Cobra Award.
In the early 1990s Huynh also had some success as a playwright, and in 1990 he was awarded a Creative Writing Fellowship from the National Endowment for the Arts. In 1997, Huynh published his second book, Water Buffalo Days. He was the first Vietnamese to write fiction and non-fiction in English.