Holly's frock, complete with plunging neckline that showed off her famous assets, sparked 139 viewers to complain to the BBC.
Holly Willoughby in the dress that led to 139 complaints
A spokesman for the Beeb said: "We're sorry if some viewers found Holly's dress to be unsuitable," a BBC spokesperson said.
"Holly enjoys fashion and we felt the dress she wore for the live final of The Voice UK was glamorous and wholly appropriate for the occasion."
The Voice UK final - which saw Andrea Begley crowned the winner - pulled in an average of 7.24m viewers, its highest ratings since May but below the show's 8.04m peak.
If you were one of the 139 people who complained about Holly's dress, you may want to look away now...