Work on the pool, which was completed in six weeks, included a new roof, internal ceiling, lighting and heating.
Royston Councillors Tim and Tracey Cheetham opened the renovated pool area.
Coun Tracey Cheetham said: "It’s fantastic to see Royston Leisure Centre getting the refurbishment it needs – it is an essential facility for our community.
"Tim learnt to swim at this leisure centre when he was a child and all three of our children have, and still are, learning to swim here, so this really means a lot to us."
Facility manager Martin Prest thanked the public 'for their patience and support whilst the project was being carried out.'