A spokesman for Grangetown's Tramshed confirmed Saturday's gig had been moved to The Great Hall at Cardiff University Students' Union after a "set back in the finishing touches".
He said a team had worked "24/7" in a bid to complete the renovation in time.
UB40 said it was "very much relieved" the concert was able to go ahead.
The Grade II-listed building is undergoing a Â£4m renovation into a 40-seat cinema, performance venue and cafe-bar.
A spokesman for the venue said transport would be provided to the new venue for anyone who turns up at Tramshed.
He said he was unable to comment on whether concerts planned at the venue next week would be affected.
A sold-out UB40 concert has had to move venues just hours before the band was expected on stage as the Cardiff venue is "not ready".