Plot

When his uptight CEO sister threatens to shut down his branch, the branch manager throws an epic Christmas party in order to land a big client and save the day, but the party gets way out of hand...

When the CEO (Jennifer Aniston) tries to close her hard-partying brother's branch, he (T.J. Miller) and his Chief Technical Officer (Jason Bateman) must rally their co-workers and host an epic office Christmas party in an effort to impress a potential client and close a sale that will save their jobs.

It is a few days to Christmas but you wouldn't really know it at the Chicago branch of Zenotec. Due to political correctness and the overzealousness of HR, there is very little in the way of celebrations. A quiet get-together is arranged but this is cancelled when the uptight, money-is-everything CEO (who happens to be the branch manager's sister) puts the kibosh on it. She also intends to retrench 40% of the staff at the branch. In a last ditch attempt to save the staff their jobs, the branch manager tries to land a major client. In order to show the client that they're not cold and uncaring, he (without his sister knowing) throws a huge Christmas party, and invites the client. Things could get rather festive, as long as HR don't have anything to do with it.—grantss

For months, horrible CEO Carol Vanstone has been toying with the idea of downsizing Zenotek by shutting down an entire branch. And as if that weren't enough, ruthless Carol wants to cancel the annual office Christmas party. But not if her brother, Clay, can help it. So, to save the struggling firm behind Carol's back, Clay organises an epic Yuletide gathering in high hopes of landing a life-saving, multimillion-dollar contract. However, there's no such thing as a foolproof plan. As the festivities spin out of control, can Clay's bold idea salvage the department before it sinks forever?—Nick Riganas

In the opening scene, Josh Parker (Jason Bateman) is in the process of finalizing his divorce. He is the Chief Technical Officer for an IT company called Zenotek. When he gets to work, we meet his coworkers - Mary (Kate McKinnon) is the prudish Human Resources Administrator who clashes with people in the office like Meghan (Jamie Chung), who keeps her top unbuttoned, and Jeremy (Rob Corddry), who is a grumpy jerk. Alison (Vanessa Bayer) is single after her husband cheated on her, and Nate (Karan Soni) pretends to have a girlfriend so the other guys won't bother him.

Josh goes to meet with his friend/coworker Tracy Hughes (Olivia Munn), who is developing a new software program for the company. They have an obvious chemistry between them, but Josh never had the guts to make a move.

Josh leaves work with his buddy Clay Vanstone (T.J. Miller), who is the branch's manager, to go Christmas shopping for people in the office. They pass by the Clark Street Bridge as it splits up, and Clay muses as to how fast one would have to go in order to make the jump. They mess around in a department store, and Clay ends up knocking over the Christmas tree in the lobby.

Alison is talking to Fred (Randall Park), an awkward guy from accounting, just as the company's CEO and Clay's sister Carol (Jennifer Aniston) comes stomping in. The other employees are terrified of Carol 'the Dragon Lady' as she rips off Christmas decorations. She gathers Clay, Josh, Tracy, and others for a meeting. Carol says that the company's sales have decreased this year, and she has recently been closing branches. Tracy pitches her program, which is meant to let users access the internet from anywhere they are. Mary then pulls out a cheese platter for an office Christmas party (or "non-denominational mixer"), but Carol immediately shoots down the idea of throwing a party because it's a waste of money. She orders Clay to cancel it.

Clay goes to vent in his office, and Josh and Carol follow. Clay and Carol resent each other since Carol was always bitter that their father passed the company down to Clay instead of Carol. They try to convince her not to shut down the branch so that people won't lose their jobs. Carol tells the guys that if they can close a contract with a potential client, she will let everyone keep their jobs.

Josh, Clay, and Tracy meet the client, Walter Davis (Courtney B. Vance). They give him their pitch, but he remains uninterested in working with them since he is not a fan of Zenotek's culture. As he is walking away, the three resort to secretly throwing the party so that Walter can see that they are people worth working with. Clay invites Walter, who agrees to go check out the party. The three then send out invites and rally to get everything ready in five hours.

Carol stops at Josh's apartment on her way to the airport. She doubts that Walter will agree to work with Zenotek, so she offers Josh a job at a New York branch with double the salary and benefits. He feels conflicted since that would mean abandoning Clay. Carol leaves to let Josh think about it.

Josh returns to work as the party begins. He has enlisted in trusty security guard Carla (Da'Vine Joy Randolph) to make sure things are under control, while Joel (Sam Richardson) is the DJ. Nate, desperate to prove that he has a girlfriend, has hired an escort named Savannah (Abbey Lee). He pays her pimp Trina (Jillian Bell), who is having aggressive mood swings. Clay gets his Santa suit on and slides down the stairs, causing him to crash. He reveals to Josh that he used the last of his money ($300,000) as padding, which he plans to give to everyone at the party as bonuses.

Walter shows up at the party. Josh and Clay do what they can to make sure he's having a good time, but he appears disinterested. While Josh is doing an eggnog luge from an ice sculpture that makes it look like he's blowing Santa, Walter leaves and is seen looking upset while talking to Mary. Josh and Tracy then put on a performance where they dress up in big snowman costumes. They later go up to the roof to smoke a joint, but they end up getting locked out.

Alison and Fred go somewhere quiet to talk. They start to hook up in a playroom for kids, but it gets weird because Fred starts talking like a little kid and it turns Alison off, causing her to leave.

Nate wants to show off Savannah to his coworkers, but she tells him that the $200 he gave Trina was only for an hour, and he has to pay $2,000 if he wants her to stay the rest of the night. Nate runs across the street to an ATM while Savannah sells cocaine to the guys that make fun of Nate. She leaves a bag near the snow machine, and Mary unknowingly grabs it and puts it in the machine. As Walter decides to go home, the machine sprays coke all over his face. He gets high and goes to find Clay so they can get trashed.

Josh and Tracy are talking about how he never made a move on her because he was nervous after he split up with his wife. They are about to kiss when a drunken Jeremy goes upstairs to pee. They take the opportunity to run back to the party where they find Clay and Walter partying. Walter declares to everyone that he loves Zenotek and that he wants to work with them. Everyone cheers now that they think their jobs are saved.

Carol's flight gets cancelled due to blizzard conditions. She is taking an Uber back home when the driver Lonny (Fortune Feimster) starts chatting her up. When Carol mentions she is CEO of Zenotek, Lonny mentions that she dropped people off at that place for a sick party.

A now enraged Carol returns to Zenotek and finds people throwing company property out the window, almost crushing her. She chastises Clay for throwing the party until Josh tells her that they closed Walter's contract. Moments later, they find Walter about to swing from some Christmas lights after Clay made a comment about it. The lights break and Walter falls face-first onto a filing cabinet. He gets taken to the hospital, and Mary then mentions to everyone that Walter had told her earlier that his own branch had fired him, meaning he never had a contract to give Zenotek. Carol berates the team and mentions to Clay that Josh was considering taking the job with her in New York. A heartbroken Clay leaves.

Nate finds out that Savannah gave one of his co-workers a handjob in the bathroom. He demands his money back, right as Trina shows up outside and overhears. She threatens Nate with one of her bodyguards until Clay steps out to chug a bottle. Savannah tells Trina that he's rich and an idiot, so they don't have to waste time on Nate. Clay joins the ladies to continue partying.

Josh tries to explain his situation to Tracy, who reveals that Carol also approached her to work in New York (but with triple the perks), but Tracy turned her down because she likes where she is. Josh resolves to go find Clay, but they learn that he went off with Trina and Savannah. Nate is forced to admit to everyone that he hired a prostitute, but it doesn't matter since he can help locate Clay by pinning the signal on his phone.

Mary brings her minivan around to pick up Josh and Tracy to go find Clay. Carol reluctantly joins them. They find him at a sleazy nightclub. He has been spilling his guts out to Trina about his job, which she sympathizes with because her own job is stressful. He mentions that he has $300K on him, but his slurring makes Trina think he said he has it in a personal safe. They head off with Savannah to his place to get the money. Carol fights off Trina's bodyguards before the four of them have to go get Clay.

Josh drives the minivan as he knows where Clay is headed - to make the jump over the Clark Street Bridge. He chases him through the city and catches up. Josh and Carol try to get Clay to pull over, with Josh apologizing for considering taking the other job. Josh tells Clay that he'll jump the bridge with him. Carol disagrees and takes control of the wheel to swerve away from the bridge. Clay misses the bridge but still jumps off a ramp and crashes the car into an electrical grid.

The crash causes a citywide internet outage. Clay, Trina, and Savannah are taken to the hospital. Now knowing their jobs are officially in the toilet unless something is done, Josh, Tracy, and Mary rush back to Zenotek to fix the problem. Using Tracy's new program, they are able to get on the internet and restore the connection to the city. Carol gets the notification on her phone from the hospital, meaning their jobs are all safe. Josh and Tracy kiss, and so do Nate and Alison after having formed a connection that night. Meanwhile, Clay and Carol reconcile and put their differences aside to enjoy the holiday. Walter enters their room and thanks Clay for showing him a good night, and that he will be joining the Zenotek team.

The team goes to pick up Clay and Carol from the hospital for breakfast. Despite the doctor advising Clay not to drink alcohol, that's exactly what they all plan to do.