He was educated at Selwyn College, Cambridge and received his Bachelor of Arts in English in 1974. In 1977 he obtained from Birmingham University his Master of Arts in 1977. O'Brien attended Hull University from 1976 to 1979 and gained from Leeds University a Post-Graduate Certificate in Education in 1981.
O'Brien worked as a teacher at Beacon School, Crowborough, East Sussex from 1981 to 1989. He then was fellow in creative writing at the University of Dundee in 1989-1990. Later he was founding editor at The Printer’s Devil literary magazine, Brighton, East Sussex with Stephen Plaice in 1990.