"I wouldn't miss performing at The BRITs, because usually when people perform, their album and single sales go way up the chart, so looking forward to that especially... I'll be there with bells on," Capaldi said in a news release.
Mabel said she's also excited to take the stage at the O2 Arena.
"So many legendary people have performed at The BRITs, so it really is an honor and a dream come true!" Mabel said.
The artists will join previously announced performer Celeste -- the 2020 BRIT Rising Star Award winner -- at the event honoring excellence in music in Britain.
The ceremony is scheduled to air live on British broadcaster ITV.
Actor and comedian Jack Whitehall is hosting the gala.