The centre, built by the former City of Durham Council, transferred to Durham County Council in 2009 and is used by around 3,500 people each month.
Stephen Verde, the longest standing member of the centre’s gym, was invited along to help staff mark the special occasion, on Monday 22 February.
Stephen, a 60 year old retired social worker from Waldridge near Chester-le-Street, joined with his wife Penny 20 years ago.
Stephen tries to go every day, often with his daughter Sarah Taylor who is also a member.
He said: “I can’t believe it’s been 20 years since I became a member, I went to a birthday party at the centre with my wife and we both joined.
“The equipment has certainly improved over those years!
“I continue to go most days so I have a good rapport with the staff who all know me.”
Nigel Dodds, the county council’s strategic manager for culture and sport, said: “It’s fantastic that Stephen has stayed with us and been such a loyal member.
“Well done to all of the staff at Abbey who work really hard to make it such a much-loved and well-used facility.”
The site is one of ten leisure centres run by the county council.
Whether it’s fitness, sport, or family fun that inspires your visit, Abbey Leisure Centre has a great range of activities on offer including a gym, exercise classes and loads of activities for children to enjoy.
The centre’s sports hall and courts are also available to hire for badminton, basketball, football, squash or table tennis.