Five years after the first film, Lou Dorchen and Nick Webber have become rich and famous, with Lou becoming a multi-billionaire and Nick being a popular music singer. At Lou's celebratory party, Lou is shot in the groin. Jacob (Lou's son) and Nick drag him to the hot tub time machine and activate it in order to travel back in time to find and stop the killer. When they wake up, they find themselves ten years into the future, where Jacob is in charge of Lou's mansion. After determining that they are in an alternate timeline where Lou's killer is from this future, they go to their friend Adam Yates's home, only to meet his son Adam Yates Stedmeyer (Adam Jr.) who is engaged to a girl named Jill.
Lou suspects his rival Gary Winkle is the killer, however, he learns Gary actually made his own fortune off of some land Lou could have bought. They party at Gary's nightclub, where Adam Jr. takes hallucinogens for the first time. The next day, they attend the popular television game show Choozy Doozy, where contestant Nick is required to have virtual reality sex with a man. As Lou suggested the idea, he is obligated to participate, but uses his "lifeline" to switch with Adam Jr. Jacob becomes disillusioned with the misadventures and leaves the group to get drunk at Gary's club and to then commit suicide by jumping off an extremely high building. Lou makes amends with him and prevents his suicide.
When the guys see a news report where Brad, an employee of Lougle, invents nitrotrinadium, the ingredient that activates the hot tub time machine, they suspect he is the killer. At Adam Jr's wedding, Jacob talks with Brad and realizes he is not the killer but that he invented the chemical after being inspired by Lou's words. Jill, who is upset about Adam Jr's partying, has sex with Lou, but when Adam Jr. finds out, he steals the nitrotrinadium and goes back to the past. Jacob, Nick and Lou return to the mansion, but are too late to stop Adam Jr. As the guys sit in defeat, Jacob realizes that because the chemical has appeared in the past, it now exists in the future. They return to the present and stop Adam Jr. from shooting Lou after Lou apologizes to him.
Following this, Nick apologizes to Courtney as Lou tells his wife he wants to go to rehab for his drug addiction. Adam Jr. meets Jill for the first time. The more self-confident Jacob approaches Sophie (his girlfriend in the future) and convinces her to join him in a relationship. As Lou, Nick, Jacob, and Adam Jr. return to the hot tub, Lou's head is shot off by a Lou (or Adam Sr. in the Unrated version) dressed in a minuteman costume. Patriot Lou informs them there are multiple Lous anyway and invites them to "make America happen." During the closing credits, the guys are seen exploiting the time machine to change history.
John Cusack, who played Adam Yates in Hot Tub Time Machine (2010), has an uncredited cameo appearance in this film's unrated version.
Principal photography began in New Orleans on June 5, 2013. On January 31, 2014, it was announced that the film would be released on December 25, 2014. On October 14, 2014, the film's release date was pushed back to February 20, 2015.
Hot Tub Time Machine 2 grossed $6 million on its opening weekend, finishing 7th at the box office.
The film went on to gross a total of $13.1 million, against a $14 million budget, which was less than the opening weekend of the original film.
Rotten Tomatoes gave the film an approval rating of 14% based on 100 reviews; the average rating is 3.3/10. The site's critical consensus reads, "A shallow dip overflowing with juvenile humor, Hot Tub Time Machine 2 is a lukewarm sequel that's healthiest to avoid." Metacritic gave the film a score of 29 out of 100 based on 31 reviews, indicating "generally unfavorable reviews". Audiences surveyed by CinemaScore, gave the film a grade of "C−" on an F to A+ scale.
The film was also singled out by GLAAD for its "outright offensive depictions of LGBT people" and defamatory homophobic humour.
Hot Tub Time Machine 2 was released on DVD and Blu-ray on May 19, 2015 with a "Hotter and Wetter Unrated Cut" on the Blu Ray that includes additional scenes including a cameo from John Cusack that cannot be seen in the film's theatrical edition.