Mountjoy enjoyed a resurgence in his 40s, and at the age of 46 he defeated Stephen Hendry in the final of the 1988 UK Championship. He followed up by also winning the next ranking event, the 1989 Classic, and by the end of the 1988–89 season he was back in the top 16, where he remained until 1992. His world ranking peaked at number five in 1990–1991. He also won five Welsh Professional Championship titles during his career.