At first writing conventional space opera, he later began to experiment with the novel form. His 1968 novel Stand on Zanzibar, about overpopulation, won the 1969 Hugo Award for best science fiction novel. It also won the BSFA award the same year. The Jagged Orbit won the BSFA award in 1970. His novel The Sheep Look Up (1972) was a prophetic warning of ecological disaster.Brunner is credited with coining the term "worm" in his 1975's proto-Cyberpunk novel The Shockwave Rider, in which he used it to describe software which reproduces itself across a computer network. His pen names include: K. H. Brunner, Gill Hunt, John Loxmith, Trevor Staines, and Keith Woodcott.
As well as his fiction, he wrote many unpaid articles in a variety of publications, particularly fanzines, but also 13 letters to the New Scientist and Physics Education (1971) volume 6 pages 389-391 "The educational relevance of science fiction" by John Brunner. Brunner was an active member of CND and wrote the words to The H-Bomb's Thunder which was sung on the Aldermaston Marches. He was a linguist and Guest of Honour at the first European Science Fiction Convention Eurocon-1 in Trieste in 1972.