A pair of underachieving cops are sent back to a local high school to blend in and bring down a synthetic drug ring.
Eric (Dave Franco) is the high school’s dealer. The PE coach (Rob Riggle) is the supplier.
A big deal goes down in the end which involves the supplier, the dealer, our two heroes Schmidt (Jonah Hill) and Jenko (Channing Tatum), and the biker gang from the duo’s first botched-arrest.
Just when things turn ugly for the good guys, it is revealed that the two of the bikers are really DEA undercovers, and happen to be Johnny Depp and the other dude from the original 21 Jump Street TV show. They cause enough of a distraction, before getting killed, that Schmidt and Jenko are able to get away.
Schmidt and Jenko chase the PE coach, who takes Schmidt’s love interest as a hostage. Jenko is shot by the coach, so Schmidt has to overcome his cop-deficiency to save his love. He shoots the coach in the genitals, and the movie ends.
The film opens in “The Year 2005”. Schmidt (Jonah Hill) gets off the bus at high school, dressed like Eminem. It’s prom week, and he stops a pretty, popular girl in the hallway and tries to ask her to prom. She turns him down hard, and Jenko (Channing Tatum), a jock in a letterman’s jacket, mocks Schmidt.
Just then, Jenko is called to the principle’s office. The principle tells Jenko that he won’t be allowed to go to prom because his grades are too crummy. Jenko was going to be crowned prom king, so he’s pissed.
Cut to “7 Years Later”. Schmidt is entering the police academy. As he walks in, he sees that Jenko is part of the same training group. They quickly realize that Jenko is great at the physical challenges while Schmidt excels at studying, so they team up to help each other pass, and they become friends.
Before long, they graduate as full-fledged police officers, and they say, “Get ready for a lifetime of being badass mother f$%#ers!” Cut to Schmidt and Jenko riding police bicycles around a park. Their days are spent stopping kids from feeding the ducks, so they are extremely excited when they see a motorcycle gang called the “1%ers” smoking weed. Schmidt and Jenko shake them down, and while the gang members mock and laugh, Schmidt finds a bag of coke in one of their saddlebags.
The gang members take off, and Schmidt and Jenko each pursue one guy. Schmidt is afraid to shoot his gun, so he gets bowled over and his perp escapes, but Jenko catches his man. Schmidt and Jenko celebrate like crazy.
Back at police headquarters, their captain informs Schmidt and Jenko that their arrest was voided because they forgot to read the biker his Miranda rights. It turns out that Jenko doesn’t even know the Miranda rights, so the captain sends them off to an undercover program the department is resurrecting.
Schmidt and Jenko pull up to “21 Jump Street”, an old abandoned Korean church. They are met by Captain Dickson (Ice Cube), who explains that Schmidt and Jenko and the other recruits will be going undercover in various high schools. No one at the schools knows about the police program, so it’s very important that they don’t get expelled.
Captain Dickson pulls Schmidt and Jenko aside to talk about their specific assignment. They will be going undercover in Sagan High School because a new designer drug has recently taken hold among the student populace. Dickson shows them a YouTube video of one of the students taking the drug. The kid proceeds through the stages of giggling, tripping out, extreme over-confidence, then total craziness. Apparently, the kid has since OD’d and died, so it’s important that Schmidt and Jenko infiltrate the dealers and find the supplier fast.
Schmidt and Jenko have to pose as brothers and stay at Schmidt’s parents’ house. As they move into Schmidt’s old room, Schmidt tells Jenko that he’s afraid they won’t be friends anymore when they go back to high school, since they were never friends in high school before. Jenko says not to be silly, it’s just an assignment. Besides, Jenko is sure he can show Schmidt how to be cool.
On the first day of school, Jenko tells Schmidt to use only one strap of his backpack, and they get a sweet muscle car from the police impound lot. But when they arrive at Sagan, all the kids use two straps and there are a bunch of cliques that Jenko doesn’t recognize, like the Emo kids.
Schmidt is distracted when he sees a really pretty girl riding her bicycle, and Jenko gets in a fight with the eco-friendly kids who aren’t impressed with his gas-guzzling car. Jenko punches one eco kid in the mouth, and it turns out the kid is gay, so everybody thinks Jenko committed a hate crime. Schmidt and Jenko are pulled into the principle’s office and put on warning. In the process, they mix up their fake identities, so now everyone thinks that Schmidt is the super-athlete and Jenko is in all the advanced chemistry classes.
Schmidt heads off to drama class, where he sees the pretty girl again. Her name is Molly (Brie Larson), and her boyfriend Eric (Dave Franco) is the head of the eco-kids. Schmidt starts chatting up Molly and asks her where he can score the new designer drug. Molly shows him some graffiti with the dealer’s phone number. Schmidt texts the dealer, who tells Schmidt to meet him at the yearbook office.
Schmidt grabs Jenko out of AP chemistry and they head to the yearbook office. Once there, they discover that the dealer is Molly’s boyfriend Eric. Eric sells them each one hit of the drug, but he forces them to take the drugs right away in front of him. Schmidt and Jenko run to the bathroom afterward and try to vomit, but they can’t.
As they head back to class, the gym teacher stops them. He wants Schmidt to join the track team (remember, he thinks Schmidt is the super-athlete because of the mixed identities). In the middle of talking to the gym teacher, Schmidt and Jenko start tripping out on the drug. To get away, Schmidt agrees to run track.
Back in drama, Schmidt has reached the stage of extreme over-confidence. The drama teacher asks Schmidt to audition for the role of Peter Pan, and Schmidt kills it. He will be playing Peter, opposite Molly’s Wendy. But when Schmidt tries to run in the track meet after school, he has moved on to the crazy phase of the drug, and he totally messes up the meet, flinging his relay baton across the finish line. The eco-kids are watching from the stands, and they think Schmidt is hilarious.
Back at 21 Jump Street, Schmidt and Jenko are able to draw a chart for Captain Dickson with all the eco kid dealers, but they don’t know who the supplier is yet. The other undercover cops have already made a bunch of busts in their high schools, so Dickson tells Schmidt and Jenko to hurry it up.
Jenko is pissed that he’s not cool anymore. Apparently, the cool thing now is to be smart and tolerant, so Schmidt is far more popular. Schmidt thinks they should throw a party to earn Eric’s trust. He calls Molly and they laugh and joke on the phone. She agrees to invite everybody to the party. Schmidt and Jenko give Schmidt’s parents a trip so they’ll go out of town, then they buy a ton of alcohol and steal a bunch of drugs from the evidence locker. Jenko invites the AP chem nerds to the party as well, because he has plans to bug Eric’s phone.
Everybody shows up to the party and Jenko successfully grabs Eric’s phone, but before he can return it, Eric starts leaving because a bunch of thugs from another high school have arrived. To stall him, Schmidt gets in a fight with the thugs. Jenko helps out, and Schmidt actually wins the fight, only to realize he’s been stabbed in the shoulder. Jenko pulls out the knife and everybody keeps partying.
Meanwhile, Schmidt’s parents realize they forgot their cellphone, so they come home and bust up the party. Everybody runs away, but Jenko has successfully bugged Eric’s phone, and Eric brings Schmidt on board as a dealer.
Schmidt brings all the drugs to Captain Dickson and carries cash back to Eric so he thinks Schmidt is doing a good job. Eric still hasn’t introduced Schmidt to his supplier, however. Meanwhile, Schmidt keeps flirting with Molly, and Jenko spends his time blowing stuff up with the chem nerds.
While Schmidt is hanging out with the eco-kids and Jenko is chilling with the nerds, Jenko uses the mic on the cellphone to eavesdropping on Eric. Schmidt and Molly walk into the room where Eric’s phone is charging, and Jenko is surprised to hear Schmidt asking Molly to prom. He’s even more surprised when Molly accepts. But then Eric and the rest of the eco-kids come inside and start ragging on Jenko. Because he likes being cool, Schmidt joins in, calling Jenko retarded.
Back at 21 Jump Street, the other undercover cops tell Schmidt and Jenko that the designer drug is spreading to their schools. Jenko hears via his wiretap that Eric is setting up some kind of big exchange.
Back at school, Schmidt is about to go onstage for his starring role as Peter Pan. Jenko says they have to intercept the exchange. They see Eric driving off, but their muscle car has been booted for parking in the handicap space. They steal the Driver’s Ed car instead and follow Eric.
Eric meets up with the 1%er gang and hands them a piñata full of drugs. Schmidt and Jenko follow the 1%ers, but they are pissed at each other and Jenko keeps using the teacher brake in the Driver’s Ed car to screw with Schmidt. They end up slamming into one of the bikers, and now instead of following the bikers, they are being chased. A huge car chase ensues where Jenko and the 1%ers shoot at each other, and finally Schmidt chokes again, failing to shoot one of the bikers. Schmidt and Jenko start screaming at each other – Jenko says that Schmidt is in too deep, he is actually filling out college applications like he gets to live his life over again, and Schmidt says “At least I know my Miranda rights, you idiot.”
Schmidt runs back to the high school, but the play has already started. When he pushes his way on stage, Molly is embarrassed and says she never wants to see him again. Even worse, Jenko jumps on Schmidt and they get in a big fistfight. The principle expels them.
Back at the church, Schmidt says “Aren’t you going to yell at us?” Captain Dickson says, “Nope, I’m just going to fire you.” Schmidt keeps trying to call Molly, but she won’t answer. Jenko packs his stuff to move out of Schmidt’s house. He tells Schmidt, “You know what’s sad? I actually thought we were brothers. I would have taken a bullet for you.”
Just then, Eric rolls up in his car. He says, “Get in. Both of you.” He takes Schmidt and Jenko to a deserted alleyway and pulls out two guns. He starts listing all the suspicious things Schmidt and Jenko have done, and they think Eric is going to shoot them, but then Eric explains that after their on-stage fistfight, he knew for sure they weren’t cops. He gives Schmidt and Jenko the guns and asks them to help with a big meeting between Eric’s dealer and the 1%ers.
The big meeting is going down at prom. Schmidt and Jenko help each other get dressed, and Schmidt asks Jenko if he’ll be his date. They roll up to prom the way Jenko always imagined, in a white limo with doves flying out. They also bring the nerds and a bunch of hookers for dates.
Schmidt sees Molly and he tries to confess everything to her, but she’s all messed up on the designer drug. Eric takes Schmidt and Jenko to the meet, and they realize that the supplier is the gym teacher. The nerds are taping the whole meeting remotely, but Schmidt and Jenko are worried they’ll be recognized by the 1%ers. At first, everything is going okay, but then Molly reaches the crazy phase of her drug trip and she starts pounding on the door, calling Schmidt a cop. Everybody pulls their guns.
Molly busts inside and the gym teacher takes her hostage. Schmidt and Jenko are forced to lay down their guns, and they’re about to get shot in the face when two of the 1%ers reveal that they are undercover DEA agents. They’ve been infiltrating the 1%ers gang for five years, and now Schmidt and Jenko have screwed everything up. (One DEA agent pulls off his fake nose, revealing himself to be Johnny Depp in a cameo). A huge firefight breaks out and both DEA agents get shot in the neck. As they lay dying, Johnny Depp tells his partner, “I’m sorry for how I treated you when we were undercover. The only approval I need is from my best friend.” Schmidt is touched.
The gym teacher grabs Molly and the bag full of cash and takes off. The 1%ers chase after him, and Schmidt and Jenko follow the 1%ers. A chase scene ensues where all three groups speed around the city in limos shooting at each other. Schmidt and Jenko are running out of ammo, but Jenko remembers his AP chem lessons and mixes potassium nitrate from the shotgun shells with lithium batteries, throws it all together in an alcohol bottle, and chucks it into the 1%ers limo. The 1%ers explode, and the blast causes the gym teacher’s limo to crash as well.
As they chase after the gym teacher on foot, the gym teacher shoots at Schmidt. Jenko jumps in front of the bullets, taking two in the chest and one in the arm. He’s wearing a bulletproof vest so he’s not too badly hurt, but that leaves Schmidt to apprehend the gym teacher. This time, Schmidt doesn’t choke. He shoots the gym teacher right in the penis, and both Schmidt and Jenko recite the Miranda rights.
Schmidt and Jenko apologize to each other, and then Schmidt apologizes to Molly. Schmidt and Molly kiss. Then Schmidt and Jenko return to the 21 Jump Street church in triumph. Captain Dickson gives them a framed copy of their first arrest report, then informs them that their next assignment will be going undercover at college. Schmidt shouts “Yes!” and Jenko shouts “No!”.