The judge was listening to Craig Revel Horwood’s verdict on Dr Ranj’s Quickstep when he tumbled from behind the judges’ desk.
Viewers saw his hands flailing in the air before disappearing from sight.
As this was happening, Craig was telling Dr Ranj that his posture was poor.
The other judges gasped and host Tess Daly told viewers: “Bruno just fell off his chair. Are you all right my darling?”
“I’m sorry Craig,” Bruno said, before agreeing with Craig’s verdict. “It was very slow, yes,” he said of the dance.
However, Bruno’s fall was not the only unexpected moment of the evening.
Kate Silverton nearly came a cropper after tripping as she came down some stairs during her performance.
The BBC newsreader, who was dressed as Jessica Rabbit, had flashed her leg through a curtain but then stumbled as she made her way to meet partner Aljaz Skorjanec.
However, the mishap didn’t matter when it came to the judges’ critiques, scoring 29 out of 40.
Darcey Bussell said of her Foxtrot: “Don’t worry about that little stumble, that was divine”, while head judge Shirley Ballas said the newsreader had the “sensuality” of Jessica Rabbit.
On the leaderboard, it was another unsurprising night at the top, as Steps singer Faye Tozer lead the contestants with a score of 36 for her Quickstep to ‘You’re The One That I Want’ from ’Grease.
She was followed by former Pussycat Doll Ashley Roberts with 35 points for her ‘Dirty Dancing’-themed Salsa.
However, there were some massive improvements from Seann Walsh, Graeme Swann and Stacey Dooley, who all managed to score over 30, following heavy criticism on last week’s show.
The next couple will leave the dancefloor during Sunday’s results show, airing at 7.45pm on BBC One.