The Someone Like You singer has been secretly booked as the star turn for the ITV1 show's Wembley Arena bash on December 11.
She was hand-picked by Simon Cowell in February after her stunning Brits performance.
Next month's gig — in front of up to 20million TV viewers and 10,000 audience members — will be the 23-year-old's first since being diagnosed with vocal cord haemorrhage in October. It forced her to cancel US and UK shows and she had surgery in America.
Last week she claimed in her blog to be "on the mend".
A source last night confirmed she planned to honour her X Factor booking and was resting in preparation.
They said: "Her management said this week she is still planning to make it. It's amazing news for fans and viewers."
Adele is due to perform a duet with one finalist — which insiders say could be Amelia Lily or Marcus Collins if they make the final three.
ITV chiefs are planning on making it the biggest X Factor final yet. Other acts booked include Coldplay, who are tipped to sing with Janet Devlin if she gets through, and Michael Bublé who could be a solid partner for Marcus.
There were rumours that Cowell, 52, could appear but a source close to the mogul said last night: "He's not coming — unless he changes his mind at the last minute."
THREE more reasons to watch The X Factor final – Adele, Coldplay and Michael Buble.
The three acts are lined up to perform on the ITV1 show’s grand final on December 11, marking Adele’s first public appearance since the 23-year-old’s career-saving throat op in the US.
I’m told: “Simon Cowell personally approached Adele and it’s a massive coup she’s agreed to appear.
“The final promises to be the most exciting to date.”
This would be a huge coup for Cowell, as the article claims, especially considering the circumstances surrounding the claimed performance. Viewing figures would go through the roof.