Darcy O'Brien was born in Los Angeles, the son of Hollywood silent film actor George O’Brien and actress Marguerite Churchill.
O'Brien attended Princeton University and University of Cambridge, and received a master's degree and doctorate from the University of California, Berkely. From 1965 to 1978 he was a professor of English at Pomona College. In 1978 he moved to Tulsa, and taught at the Univesity of Tulsa until 1995.
O'Brien was married three times and had one daughter named Molly O'Brien.
O'Brien died of a heart attack in Tulsa on March 2, 1998.