PLOTSeven years after escaping Guantanamo Bay, and two years after they have last spoken, best friends and roommates Harold Lee and Kumar Patel have gone their separate ways. Harold has given up smoking cannabis, become a successful business man on Wall Street and married his Latina girlfriend Maria. Kumar, on the other hand, is poor and still lives in the messy apartment he once shared with Harold. Kumar got kicked out of medical school because he failed a drug test. Kumar has recently been dumped again by his girlfriend Vanessa, who arrives at Kumar’s apartment to inform him that she is pregnant with his child. Maria’s father and Harold’s father-in-law Mr. Perez decides to stay at Harold and Maria’s house for Christmas. Mr. Perez, who does not like Harold, also brings over his prized Christmas tree that he has been growing for eight years, and gives Harold a short lecture about the tree’s importance. Kumar receives a package with Harold’s name on it at his apartment and decides to deliver it to Harold. At Harold’s house, they discover the item inside to be a large marijuana joint.
Kumar lights it up, but Harold throws it out of the window, only for it to magically land in the tree and burn it down. Harold learns that Kumar’s new friend Adrian is attending a party with a Fraser Fir Christmas tree, and promises to drive him to the party on the condition that he can have the tree. Harold, Kumar, Adrian, and Todd (Harold’s new best friend) arrive at the party, where a girl named Mary attempts to seduce Harold. It turns out that Mary is the daughter of a Russian mob kingpin named Sergei Katsov, who sends two of his men to kill Harold and Kumar, believing that they were trying to rape his daughter. The duo make it out of the building without the Christmas tree and run into their friends, Rosenberg and Goldstein, for the first time in years. Harold and Kumar plan to steal a tree from a church, but end up participating in a Christmas show featuring Neil Patrick Harris, who they thought had died after being shot outside a Texas whorehouse seven years ago. Harris reveals that he did die but Jesus Christ kicked him out of Heaven. Revealing that he can now read their minds, Harris hooks the pair up with a Christmas tree and a Wafflebot before sending them off.
The two make their way to Harold’s house to put up the tree, but end up being kidnapped by two of Katsov’s men, and are saved by Wafflebot. After accidentally shooting Santa Claus in the head, Kumar gives him emergency surgery. In exchange for saving his life, Santa agrees to fly them back home in his sleigh, and reveals that he sent the package to reunite the friends. Harold arrives home to encounter Mr. Perez, who is angered when he discovers his Christmas tree is gone. Harold finally stands up to him, explaining that he may not be the perfect son-in-law, but he is the perfect guy for Maria. Mr. Perez says that he always knew Harold was a nice guy, he just wanted to make sure that he had “cojones” before accepting him into his family. Harold and Kumar rekindle their friendship, Kumar and Vanessa rekindle their romance, and Kumar tells Vanessa that he will re-take the exams to become a doctor for the sake of their child. Maria discovers that she is pregnant on Christmas morning and that Santa has left a replacement tree in their lounge. Harold decides to smoke weed again, and he and Kumar share a joint again for the first time in years.