Des Tennant was born in Aberdare and attended the town’s Boys’ Grammar School, where he played both football and rugby. He began his football career as a junior with Cardiff City, when he was capped by Wales at youth level. After making 31 appearances in the Southern League for Barry, Des Tennant joined Brighton & Hove Albion making his Football League debut in the 1948–49 season. Although primarily a right back, he played in a variety of positions, and was the club’s top scorer in his first season with 11 goals in all competitions. Nicknamed “The Tank”, he was described as a “very important player” in the Brighton team promoted to the Second Division for the first time in 1957-58. By the time he retired in 1959, having lost his place to Tommy Bisset, he had played 424 matches and scored 47 goals in all competitions. He then joined the coaching staff at the club, later acting as chief scout.
After leaving football he worked for the ambulance service and kept a pub before retiring to his native South Wales.