All spoilers for the previous films are unmarked
Taking place shortly after The Kissing Booth 2, Elle (Joey King) is planning to spend the last summer before college alongside her best friend, Lee (Joel Courtney), her boyfriend, Noah (Jacob Elordi), and Lee's girlfriend, Rachel (Meganne Young), at the Flynn family's beach house. Elle has chosen to attend Harvard so she can be with Noah, but feels guilty of abandoning Lee. To make up with him, she invites him to do a bucket list of activities they dreamed as kids, all in the span of a single summer. She soon learns how exhaustive it can be to balance her role as a friend to Lee and a girlfriend to Noah, something that isn't helped when she reunites with Marco (Taylor Zakhar Perez). To top it off, she struggles to accept the fact that her father (Stephen Jennings) is dating another woman, Linda (Bianca Amato). Can Elle juggle the responsibilities and face new realities, or will she break down and lose everything she has?
The film also stars Maisie Richardson-Sellers as Chloe, Noah's friend from Harvard, and Molly Ringwald as June, the Flynn brothers' mother.
The Kissing Booth 3 contains examples of:
- Amicable Exes: Noah and Elle become this in the end; they're happy to meet up again after six years, are both proud of the other's achievements and take a motorcycle ride together like they used to. It's even implied they might rekindle their romance.
- Artifact Title: Even more so than the second film, where the kissing booth at least has some significance to the story (it results in Lee and Rachel making up, Elle definitively rejecting Marco for Noah, and Ollie finally confessing his feelings for Miles). Here, the kissing booth has nothing to do with the plot and merely gets a cameo appearance.
- Artistic License:
- When Elle is seriously considering going to Harvard, Noah says he'll look for an apartment for them to share in Boston. However, a quick Google search will inform you that first-year Harvard students are required to live on-campus, so while second-year student Noah could live off-campus if he wanted, at best Elle would be relegated to visiting him in her spare time. It's especially weird considering that the previous film did depict Noah living in a room on-campus during his first year.
- Once again, Elle and Noah are depicted being able to walk right up to the Hollywood sign, which you can't do in real life unless all the security measures were suddenly dropped for some reason.
- Beach Episode: The film's setting is the Flynn family's beach house.
- Berserk Button: Although her anger and hurt has been building up for some time, Elle blows up on Linda because she chooses the Scottie dog token when they're playing Monopoly, not realizing that Elle always chooses that one.
- Beta Couple: Lee and Rachel have a far more adjusted relationship compared to Elle and Noah. This doesn't stop them from breaking up, if temporarily.
- Be Yourself: Mrs. Flynn tells Elle to stop sacrificing herself to let Noah and Lee be happy, and ask herself: "What do I want?" This motivates Elle to decline both Harvard and Berkeley, instead applying for the video gaming department at the University of Southern California.
- Bittersweet Ending: Elle decides to attend USC, therefore following her dream in the gaming business. In the process, she breaks up with Noah, while Lee and Rachel also amicably break up so their relationship will not stand in the way of college, and all of them drift apart. But they are reunited six years later, with Lee and Rachel having reconciled and about to marry in several weeks, while Elle is implied to also reconcile with Noah.
- Calling the Young Man Out: When Elle insults her dad's new girlfriend Linda in front of everyone over a Monopoly game and says she'll never be part of their family, Elle's father confronts her about her attitude. Elle calls her father "selfish" for dating again after her mother died, prompting Mr Evans to point out although he was also devastated by Elle's mother dying he had to stay strong to look after her and her brother, that he hasn't dated anyone else until now for his kids' sake, and that Elle isn't the only one who deserves love and happiness. It doesn't help that Linda is far from being a Wicked Stepmother and no one else has a problem with her. Elle later realizes that her dad made some good points and apologizes to Linda.
- Cassandra Truth: Noah tells Elle repeatedly that Marco isn't hanging around with her because he wants to be Just Friends, but she completely dismisses the idea until it smacks her in the face (well, Noah's the one who gets smacked, but still). When she tries to apologize for being so obtuse, Noah angrily states I Warned You.
- Cock Fight: Marco tries to initiate one with Noah over Elle, punching him in the face after Noah publicly calls him out for still pursuing Elle. However, Noah refuses to retaliate.
- Coming of Age Story: The previous films have elements of this, but this movie more fully embodies it, focusing on the protagonists facing the fact they have to say goodbye to their childhood as they prepare to attend college, including having to make difficult decisions and letting go of things holding them back from maturing. In particular, Elle learns to make decisions based around her own happiness rather than what other people want, Lee has to accept that his loved ones' lives don't always revolve around him but that doesn't mean they love him any less, and Noah realizes he has to let go of Elle so they can both pursue their own dreams.
- Demoted to Extra: Most of Elle's friends from high school, like the OMG Girls and Ollie, only make cameo appearances, since with school being over, Elle has no reason to see them often.
- Derailing Love Interests: Downplayed. Compared to the previous film, Marco is rather more aggressive in his plan to snatch Elle from Noah, even luring him into fighting publicly (he refuses to take the bait, though). After Elle rejects him outright, however, he finally takes the hint and parts ways from her amicably.
- Disappointed in You: Stated word-for-word by Mr. Evans, after Elle insults Linda at the family gathering.
- Distant Finale: The epilogue is set six years later. Elle has become the owner of a small video game company, Noah is about to join a law firm, while Lee and Rachel are engaged to be married.
- Expository Hairstyle Change: In the future, Elle sports Power Hair, showing her transformation from a Gamer Chick into a full-fledged game developer.
- Fast-Forward to Reunion: After the gang break up to attend different colleges, the film cuts to six years later, where they have all graduated. We also see what they have become since.
- Foreshadowing: Early on at the beach house, Rachel accidentally pulls off a glass doorknob on a wardrobe and Lee says he and Elle used to pretend it was a diamond when they were kids; he places it on Rachel's hand like a ring for a laugh. The ending reveals they're engaged to be married.
- Good-Times Montage: Twice. The first happens in the opening, showing Elle's trip from Los Angeles to San Francisco with Noah, Lee, and Rachel. The second is when Elle and Lee decide to do their bucket list, most of which are glossed over with a montage.
- Growing Up Sucks: Elle and Lee get hit with this hard, as they realize that graduating from high school means entering a totally uncharted territory that requires them to grow up. On example is their attempt to fulfill the very long bucket list, as a way to clean up any loose ends in their childhood and therefore move on to adult life with few regrets. Although they start off optimistically, they begin missing one milestone after another, and towards the end, realize that they will not be able to do them all, since summer is nearly over and Lee needs to pack up for his move to Berkeley.
- Handshake Refusal: Noah refuses to shake hands with Marco after losing the Mario Kart-themed race. Later, after the beach volleyball match, Marco does shake hands with Noah... but then calls him an asshole and punches him.
- Hello, Attorney!: After the six-year time skip, Noah has become a lawyer and is as attractive as ever, wearing a snappy suit. Elle in particular watches him longingly, very possibly still carrying a torch.
- High-School Sweethearts:
- Played straight with Lee and Rachel in the ending; they began dating in high school and after taking a break to attend college, they got back together and are getting married.
- Possibly played straight with Elle and Noah, though it's not confirmed that they do get back together.
- I Want My Beloved to Be Happy: Although they both still love each other Noah breaks up with Elle so she won't feel pressured to follow him to Harvard, wanting her to pursue her own dreams at a college of her choice. She's initially devastated, but it works out for both of them and it's hinted they may get back together after they're established in their careers.
- Laser-Guided Karma: After the two wedgies Lee got from Noah in the first film, he finally returns the favor with Elle's help.
- Long-Distance Relationship: Deconstructed. Despite the previous film's message of this being a feasible option, this film repeatedly shows that this is a very difficult way of keeping a relationship afloat, since not only you have to maintain a regular schedule to prevent things from going sour, but also sacrifice your priorities so you can placate your loved ones. Noah breaks up with Elle as he knows that, beyond being able to be with him, she doesn't really want to move all the way to Boston. Meanwhile, Rachel breaks up with Lee explicitly because she doesn't want to do LDR.
- Love Cannot Overcome: Lampshaded by Noah when he breaks up with Elle; although they love each other he knows she's only going to Harvard because of him rather than what she actually wants and he's concerned that if things don't work out he'll be responsible for Elle being unhappy.Elle: So that's it? The fact that we love each other means nothing?Noah: I do love you but...maybe sometimes loving each other just isn't enough.
- Love Triangle: Marco shows up again, still wanting a romance with Elle, who is back with Noah. This time it's more of a Type 4 situation, as Elle isn't interested in Marco to the point she's oblivious he still has feelings for her.
- Mascot Racer: One of Elle's and Lee's bucket list is doing a Mario Kart-themed race, with Elle dressing up as Mario, Lee as Princess Peach, and Rachel as Luigi. Noah initially dismisses it, but is hit with jealousy when Marco appears dressing up as Wario, and decides to join (although he still refuses to dress up).
- Maybe Ever After: Six years after their breakup, Elle reunites with Noah at their alma mater. It is implied, though not stated, that they will find their way to each other back, just like Lee did with Rachel.
- Oblivious to Love: Elle is painfully oblivious to the extremely obvious fact Marco is still attracted to her and is hanging around with her in the hopes of changing her mind; it takes Marco punching Noah for publicly calling him on this for her to finally catch on. Noah even calls her obliviousness "embarrassing".
- O.O.C. Is Serious Business: Chloe is normally an extremely kind and softspoken person, so Noah knows something is up when she tells him off for not doing enough to reconcile with Elle after their fight. This is because she is frustrated that her parents are divorcing without much fanfare, making her angry at people who don't seriously fight for their love.
- Parent with New Paramour: Mr. Evans is dating a woman named Linda, who immediately sets about to win the children's hearts. While Brad is easily won over, Elle is skeptical and outright tells her that she considers her intrusive to the family. It takes her father calling her out for her to finally warm up to her.
- "Reason You Suck" Speech: After inadvertently missing her and Lee's last chance to play on their Dance Dance Mania game, Lee accuses Elle of not caring about him and claims she's always chosen Noah over him. Elle is infuriated and launches into a speech of her own, lambasting Lee for being a Spoiled Brat who can't accept that their lives and friendship is changing and unloading on him about all the pressure she's felt to "make it up" to him for choosing Harvard over Berkeley. She ends it by saying she's done following the "friendship rules" Lee has always used to control her before storming off, leaving Lee in shocked tears.
- Spoiled Sweet: Chloe arrives at Los Angeles on a private yacht, something that even Noah, who lives in a Big Fancy House, is awed at. She is still a very kind and levelheaded person as ever.
- Surprisingly Realistic Outcome: The Kissing Booth films are romantic comedies - which tend to fall more on the idealistic side of things - and the movies generally have a slightly "heightened reality" feel to them. As a result, it comes off as more surprising, though logical, when Elle and Noah break up in the third act...for good. Realistically, it's highly unlikely a high school romance where the couple live on opposite ends of the country and fight constantly about everything would stay intact for the long-run, even if they both care for each other.
- Take a Third Option: Throughout the film Elle struggles between choosing Harvard (and Noah) and Berkeley (and Lee). In the end, she decides rather than making a decision to make someone else happy, she'll do what she wants; she turns down both universities to attend the University of Southern California.
- Turn the Other Cheek: When Marco punches Noah in the face and all but dares him to fight him, Noah seriously considers it for several moments before declaring "I'm not doing this" and riding off on his motorcycle.
- You Are Better Than You Think You Are: So says Chloe to Elle, to cheer her up after her breakup with Noah.Chloe: For whatever it's worth, I want you to know that I think you are an absolutely brilliant woman.
- What Happened to the Mouse?: Ashton (the guy from Berkeley that Lee becomes friends with) abruptly disappears after a few scenes, taking the subplot of Elle being slightly jealous of their budding friendship with him.
- What the Hell, Hero?: Elle's dad confronts her about being disrespectful to Linda and for accusing him of being selfish for dating her, pointing out that he'd put his romantic life on hold and worked at a job he hated so he could take care of her and Brad.
