Orlando "Brad" McVie (Vince Vaughn) and his girlfriend, Kate (Reese Witherspoon) are a happily unmarried and childfree, upscale San Franscisco couple whose respective households are somewhat similar - both bearing divorced parents, warring siblings with out-of-control kids and general awkward memories and simmering resentments from the past, which they find too embarrassing to share with each other. In an effort to avoid these families at Christmas time, Brad and Kate pretend to be engaging in charitable work and escape to exotic sun-spots, such as Fiji, to enjoy a relaxing Christmas there. Unfortunately, in the third Christmas of their relationship, Brad and Kate are trapped at San Francisco International Airport by a fogbank that cancels every outbound flight. To make matters worse, they are caught on camera and then interviewed by a CBS 5 news crew, revealing their whereabouts to the whole city and, worst of all, their families.

With no escape, their lies foiled and no excuses to make, they find themselves unable to avoid a Christmas at home with their respective families. They first visit Brad's father (Robert Duvall), then Kate's mother (Mary Steenburgen), and then Brad's mother (Sissy Spacek) and, finally, Kate's father (Jon Voight), thereby celebrating four Christmases in one day. As they brace themselves for a marathon of homecomings, Brad and Kate expect the worst, but are nevertheless unable to prepare themselves enough for what they get. As the day progresses, each discover a new secret about each other that both had been too embarrassed to tell each other about, and soon find their relationship on the verge of collapse. While Brad counts down the minutes to freedom, Kate finds herself looking at the lives of Brad's and her own siblings and realises that she does want a marriage and children of her own, the prospect of which frightens Brad. Eventually, in the final visit of the day, at Kate's father's house, Kate asks Brad to let her spend the visit on her own and claims to her family that they had split up. Meanwhile, Brad spends some time at his own father's house with just his father and realises how empty his life is without a marriage and children, and that he loves Kate much too much to leave her. He returns to her and they discuss the possibilities of having a child and getting married. The two then embark on their holiday in Fiji.

A year later on New Year's Day, the couple welcomes their first born child, a baby girl, which they have spent the last nine months hiding from their families. However, as their baby is the first born in the New Year, a news crew comes to congratulate them - once again revealing them, and their new baby to the whole city, and their families.

One of the film's executive producers, Peter Billingsley, who had a starring role as Ralphie in the 1983 film A Christmas Story, has a credited role as an airline ticket agent.

Gordon was brought in as director at the insistence of Vaughn, who had seen Gordon's documentary The King of Kong: A Fistful of Quarters, a film, Gordon points out, which, like Four Christmases, has a "traditional three-act structure."

The film began production in December 2007, during the 2007–2008 Writers Guild of America strike, which meant that no changes could be made to the script. During production New Line Cinema became a "unit of Warner Bros.", which put the film's completion at risk.

The film received negative reviews from critics. Rotten Tomatoes reports 26% of critics gave the film a positive review based on 111 reviews. At Metacritic, which assigns a normalized rating out of 100 to reviews from mainstream critics, the film holds a mixed/average score of 41 based on 27 reviews.

The Hollywood Reporter called the film "one of the most joyless Christmas movies ever" with "an unearned feel-good ending [that] adds insult to injury"; it criticized the film's script for "situat[ing] Hollywood clichés about Southern rednecks incongruously within the tony Bay Area." Variety magazine called it an "oddly misanthropic, occasionally amusing but thoroughly cheerless holiday attraction that is in no way a family film." The Associated Press said the film "began with some promise" then segued into "noisy joylessness [that] sets the tone for the whole movie"; the review noted that "Vaughn makes the movie tolerable here and there, but this kind of slapsticky physical comedy doesn't suit Witherspoon at all." Frank Lovece of Film Journal International found "no core to their characters. They just embody whatever plot machination the movie needs at any given moment", and that, "Every predictable Christmas-comedy trope gets dragged out like the string of electric lights that is pulled from the wall to whipsaw through the living room". Roger Ebert gave the film a meagre two stars, and wrote his review in the style of a pitch session between a filmmaker and his boss, whereby he derided the film's alleged lack of humour or narrative sense.

On its opening day, a Wednesday, it ranked second at the box office with $6.1 million, behind the previous week's new release blockbuster Twilight. It then went on to take the top spot each successive day from Thursday to Sunday, earning $46.1 million and ranking #1 over the entire extended Thanksgiving holiday weekend. In its second weekend, Four Christmases held on to the #1 spot, taking in another $18.1 million.

As of January 8, 2009, the film has grossed $118.6 million domestically and $154.9 million worldwide.