The centre - in the Glass Works - has been in use since April this year, with phlebotomy and ultrasound services on offer, and later joined by breast screening in May and plain film x-ray services in early June.
On Tuesday, the centre introduced bone density scanning to complete its offer.
Bob Kirton, chief of delivery and deputy chief executive at Barnsley Hospital, said: “It’s taken a lot of hard work to get the project off the ground.
“Barnsley has a really proud history, but this service will attempt to address the imbalance in health and inequality.
“We want to do three major things: improve access to healthcare for residents, give the public a better experience and to get improved health outcomes.
“The current set-up at Barnsley Hospital for breast screening in particular takes place in the car park, which is not bad but not what we want.”
The facility - which cost just under £3m - is the first of its kind in the country to be sited in a town centre retail and leisure facility.
It will allow patients to attend scans and blood tests in a more relaxed environment, encouraging those who are intimidated by a hospital to attend appointments, and help in earlier detection of disease.
Among the guest speakers at Tuesday’s opening was Professor Sir Mike Richards, who was commissioned to undertake a review of diagnostics in the NHS in 2020, and who recommended a new model - with facilities like the one in the town centre a priority.
He added: “This is a really thrilling development- the patients love it and the staff love it.
“I think this will be instrumental for other places in the country.”
Gavin Boyle, chief executive of South Yorkshire’s integrated care board, said the facility was another great example of the work between local authorities and NHS organisations.
“It will take the pressure off the hospital - 50,000 local people will have access to services here, but also 50,000 people will make their way into Barnsley town centre.”
Thanks were given to staff working at the centre, who will be working rotationally between the hospital and the new facility.
Council leader Sir Steve Houghton told the Chronicle: “We need to convince people to look at their health differently.
“Changing people’s mindsets is not an easy thing to do, but we have to do it.
“If we can do that, we can make a difference.”