Staff at Leo Leisure have tried to rescue the trapped moggy, who was first spotted last Friday.
It can be seen wandering around in the lights on the ceiling of the hall on High Street.
Staff say they have contacted the fire brigade, the RSPCA, and The Cat Welfare Group for help.
But so far, volunteers have been unable to rescue the trapped cat.
Food and water have been left in the ceiling space for the cat.
Manager at Leo Leisure, Simon Philips, said: “The cat was spotted first on Friday late in the evening.
“We thought it probably got in as we’ve got builders working around us.
“He was gone for a bit, but then on Sunday he was walking across the ceiling.
“We thought maybe he was shut in by the builders, but on Monday he was still here.
“I first called the fire bridgade, they told me I would need to contact the RSPCA.
“He’s not easy to get to, it’s high up and we can’t reach him ourselves.”
Mr Philips said he was told by the RSPCA to wait 24 hours but he is yet to receive a call from the charity.
“It’s been longer than 24 hours and no one has called us,” he said.
“He’s still here.
“On Monday night I had a call from the cat welfare group and they came out that night with a volunteer, a tree surgeon. He went up there but he couldn’t get him.
“They came out again yesterday, put some more food down for him.
“They’re trying their best, they’re a small charity.
“I think he’s safe and he’s okay. We’re doing the best we can.”
A spokesperson from Hampshire and Isle of Wight Fire and Rescue Service (HIWFRS) said: “On Monday evening the HIWFRS Control Room received a call reporting a cat inside a retail unit on the High Street in Southampton.
“The caller was informed that due to the cat not being physically trapped, as it was able to move around freely inside, it was a matter for the RSPCA.”
Since the Daily Echo visited the Leo Leisure hall, the RSPCA has confirmed that it is “working with fire and rescue to retrieve the cat”.
An RSPCA spokesperson said: “We have been made aware of a cat trapped in the ceiling space at Leo Leisure in Southampton.
“One of our brilliant inspectors [has visited the location today] with the aim of safely retrieving the cat.”
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