The two-minute film (above) will air tomorrow (17 November) before Gogglebox on Channel 4, while teaser clips have premiered across the broadcaster since Tuesday.
It follows the story of a little girl who spends the day saving a carrot stick for Santa's reindeer, only to be told by her brother: "You know there's more than one, right?" To avert disaster, the dad gets in the car and picks up a bag of carrot sticks from McDonald's to ensure the family is #ReindeerReady.
The film, created by advertising agency Leo Burnett, was inspired by the recognisable Christmas tradition of saving snacks for Santa and his sleigh-bearers, McDonald's said, and is designed to tap into the excitement and anticipation of the festive season.
Katie Parker, head of marketing at McDonald's UK, added: "The ad also reminds people that McDonald's has a role to play in providing a brief respite during the busy Christmas period - particularly when out shopping."
Parker said the film would be supplemented by secondary media activity throughout November and December, including a partnership with Snapchat.
The partnership includes a hub on the platform with three McDonald's-inspired features. The first is a game that tasks players with collecting carrots. Parker said this was a "playful reflection of the ad" through which friends and family could share scores.
The second feature is an AR lens that allows users to see a dancing reindeer through their smartphones, while the third is a series of geofilters available at McDonald's restaurants throughout the UK.
Parker said the tie-in on social media was "crucial" for ensuring the success of this year's campaign, which also includes Christmas jumpers, novelty antlers, and branded baubles.
PR is handled by Red Consultancy, which also worked with budget retailer Aldi on its Kevin the Carrot sequel.
Last year's McDonald's Christmas campaign followed Juliette, a vintage doll destined to spend another Christmas alone. It achieved close to 100,000 views on YouTube, while a follow-up ad about the chain's festive menu, featuring the doll spying on a family, has been viewed more than 500,000 times.