He left Cardiff for a tribunal set fee of £65,000, as well as a £20,000 bonus once Bennett had appeared in 40 matches for the club, in July 1984 to follow manager Len Ashurst to Sunderland, becoming only the second black player to play for the club after Roly Gregoire. He made a goal scoring debut for the club at Roker Park during a 3–1 victory over Southampton, heading past Peter Shilton after just two minutes. Bennett went on to play 369 league games with Sunderland scoring 23 goals, appearing in the 1985 Football League Cup Final, losing 1–0 to Norwich City, and the 1992 FA Cup Final, losing 1–0 to Liverpool. He was also voted the club's player of the season for the 1986–87 and 1993–94 seasons and more than 21,000 people attended his testimonial match at Roker Park against Rangers in July 1993. He left Sunderland in 1995 after eleven years at the club, joining Carlisle United.