Steadman was born in Wallasey, Cheshire, and brought up in Abergele, North Wales. From a lower middle class background, his father was a commercial traveller and his mother was a shop assistant at T J Hughes in Liverpool. Steadman attended East Ham Technical College and the London College of Printing during the 1960s, doing freelance work for Punch, Private Eye, the Daily Telegraph, The New York Times and Rolling Stone during this time. He is a patron of the Association of Illustrators. Steadman currently lives with his wife in Kent, England.