The ad features people unwrapping Christmas gifts from M&S, interspersed with shots of 'The X Factor' contestants singing 'When You Wish Upon A Star'.
Sixteen contestants appear, including Craig Colton and Misha Bryan, who closes the ad.
Walker Media placed a 60-second version of the film in yesterday's 'X Factor' results show.
Yesterday the retailer ran a promoted tweet on Twitter, which said: "Guess who will be in our Christmas ad this year? Find out during tonight's #MandSAdvert."
The ad was created by Rainey Kelly Campbell Roalfe/Y&R's executive creative director Mark Roalfe, copywriter Pip Bishop and art director Chris Hodgkiss. The director was Toby MacDonald.
The scenes and products featured will change over the course of the campaign.
Steve Sharp, M&S executive director marketing, said: "Our TV campaigns have become almost legendary – and for many customers mark the start of Christmas.
"This year we wanted to surprise them with something really special and I think we've delivered."
Follow Daniel Farey-Jones on Twitter @danfareyjones