Many fans of the group, who finished fourth in the ITV talent show, braved the cold weather to see them.
The group’s set included Taylor Swift’s Love Story, Carly Rae Jepson’s Call Me Maybe, Beyonce’s Sweet Dreams and Abba’s Winner Takes It All.
Tramps director Dean Hill said: “Union J had one of the best receptions I’ve seen at Tramps, the female fans loved them performing. They have great energy and I’m sure these lads will be back in the music spotlight soon.”
On Monday night, runner-up Jahmene Douglas will perform at Tramps and tickets are available at night-clubber.com.