McIlvanney left Kilmarnock Academy to work at The Kilmarnock Standard as a reporter moving on to the Scottish Daily Express, The Scotsman, The Observer (1963-1993), Daily Express, before joining The Sunday Times in 1993. During his time with the Daily Express he also wrote as a news reporter. He then had a long-running column on the back page of The Sunday Times sports section, from 1993 to 2016. He retired at the age of 82, citing physical demands of the job as having become too taxing.
In 1996, McIlvanney was awarded the OBE, was given the Lifetime Achievement Award 2004 by The Scottish Press Awards, and is the only sports writer to be voted Journalist of the Year. In 2005, he was included in the Press Gazette Hall of Fame.
In December 2008 he was voted into the International Boxing Hall of Fame, and he was inducted in 2009.
He has one son, Conn, and a daughter, Elizabeth.