Aldiss's father ran a department store that his grandfather had established, and the family lived above it. At the age of 6, Brian was sent to board at West Buckland School in Devon, which he attended until his late teens. In 1943, he joined the Royal Signals regiment, and saw action in Burma; his encounters with tropical rainforests at that time may have been at least a partial inspiration for Hothouse, as his Army experience inspired the Horatio Stubbs second and third books.

After World War II, he worked as a bookseller in Oxford. Besides short science fiction for various magazines, he wrote a number of short pieces for a booksellers trade journal about life in a fictitious bookshop, and this attracted the attention of Charles Monteith, an editor at the British publishers Faber and Faber. As a result of this, Aldiss's first book was The Brightfount Diaries (1955), a novel in diary form about the life of a sales assistant in a bookshop.

In 1955, The Observer newspaper ran a competition for a short story set in the year 2500, which Aldiss won with a story entitled "Not For An Age". The Brightfount Diaries had been a minor success, and Faber asked Aldiss if he had any more writing that they could look at with a view to publishing. Aldiss confessed to being a science fiction author, to the delight of the publishers, who had a number of science fiction fans in high places, and so his first science fiction book, a collection of short stories entitled Space, Time and Nathaniel was published. By this time, his earnings from writing equalled the wages he got in the bookshop, so he made the decision to become a full-time writer.

He was voted the Most Promising New Author at the World Science Fiction Convention in 1958, and elected President of the British Science Fiction Association in 1960. He was the literary editor of the Oxford Mail newspaper during the 1960s. Around 1964 he and his long-time collaborator Harry Harrison started the first ever journal of science fiction criticism, Science Fiction Horizons, which during its brief span of two issues published articles and reviews by such authors as James Blish, and featured a discussion among Aldiss, C. S. Lewis, and Kingsley Amis in the first issues, and an interview with William S. Burroughs in the second.

Besides his own writings, he has had great success as an anthologist. For Faber he edited Introducing SF, a collection of stories typifying various themes of science fiction, and Best Fantasy Stories. In 1961 he edited an anthology of reprinted short science fiction for the British paperback publisher Penguin Books under the title Penguin Science Fiction. This was remarkably successful, going into numerous reprints, and was followed up by two further anthologies, More Penguin Science Fiction (1963), and Yet More Penguin Science Fiction (1964). The later anthologies enjoyed the same success as the first, and all three were eventually published together as The Penguin Science Fiction Omnibus (1973), which also went into a number of reprints. In the 1970s, he produced several large collections of classic grand-scale science fiction, under the titles Space Opera (1974), Space Odysseys (1975), Galactic Empires (1976), Evil Earths (1976), and Perilous Planets (1978) which were quite successful. Around this time, he edited a large-format volume Science Fiction Art (1975), with selections of artwork from the magazines and pulps.

In response to the results from the planetary probes of the 1960s and 1970s, which showed that Venus was completely unlike the hot, tropical jungle usually depicted in science fiction, he and Harry Harrison edited an anthology Farewell, Fantastic Venus!, reprinting stories based on the pre-probe ideas of Venus. He also edited, with Harrison, a series of anthologies The Year's Best Science Fiction (1968-1976?)

Brian Aldiss also invented a form of extremely short story called the Minisaga. The Daily Telegraph hosted a competition for the best Minisaga for several years and Aldiss was the judge.[2] He has edited several anthologies of the best Minisagas.

He traveled to Yugoslavia, where he met Yugoslav fans in Ljubljana, Slovenia; he published a travel book about Yugoslavia; he published an alternative-history fantasy story about Serbian kings in the Middle Ages; and he wrote a novel called The Malacia Tapestry, about an alternative Dalmatia.

He has achieved the honor of "Permanent Special Guest" at ICFA, the conference for the International Association for the Fantastic in the Arts, which he attends annually.

He was awarded the title of Officer of the Order of the British Empire (OBE) for services to literature in HM Queen Elizabeth II's Birthday Honours list, announced on 11 June 2005.

In January 2007 he appeared on Desert Island Discs. His choice of record to 'save' was Old Rivers sung by Walter Brennan, his choice of book was John Halpern’s biography of John Osborne, and his luxury a banjo. The full selection of eight favourite records is on the BBC website .

On 1 July 2008 he was awarded an honorary doctorate by the University of Liverpool in recognition of his contribution to literature.

In addition to a highly successful career as a writer, Aldiss is also an accomplished artist whose abstract compositions or 'isolées' are influenced by the work of Giorgio de Chirico and Wassily Kandinsky. His first solo exhibition The Other Hemisphere was held in Oxford, UK, in August-September 2010, and the exhibition's centrepiece 'Metropolis' has since been released as a limited edition fine art print.