Set once again in the quaint town of East Great Falls, Michigan, this new installment of the American Pie series follows a group of four teenage girlfriends as they navigate the complexities of their senior year. Among them is Annie (Madison Pettis), a young woman eager to lose her virginity to her boyfriend Jason. In a series of comical misadventures, Annie finds herself in ever-increasingly embarrassing situations, including a muddy mishap while attempting to sneak into Jason's house for a late-night rendezvous. Unfortunately for her, things take a further turn when Jason's parents unexpectedly arrive with an apple pie to celebrate his college acceptance, catching the couple in a rather compromising position.
On the other hand, Stephanie Stifler (Lizze Broadway), a confident lacrosse player and proud member of the infamous Stifler family, resorts to blackmail against the school's lecherous principal, armed with evidence of his more than questionable activities. Kayla (Piper Curda) grapples with insecurities about her boyfriend Tim, obsessively checking his phone after their initial sexual encounter and questioning her standing as "the best girlfriend." Meanwhile, Michelle West (Natasha Behnam), an overachiever with a wealth of knowledge about sex toys, dedicates herself to maintaining her impressive academic record.
As summer comes to an end, the four friends unite during a lakeside party, forming a pact to achieve their individual desires before the rapidly approaching senior prom, just five weeks away. As the school year kicks off, they meet Grant (Darren Barnet), a new, charming addition to their school who first crosses paths with Michelle, leading to some amusing moments as she quite literally runs into a door while trying to get his attention.
In an emotional twist, Kayla's relationship with Tim crumbles, but Grant steps in to help her concoct a plan for revenge. Their interactions lead to unexpected connections, sparking a budding romance between Grant and Annie as they team up for schoolwork in the library. Meanwhile, Michelle’s and Stephanie’s feelings for Grant become increasingly obvious, leading to clever schemes to win him over.
The tension reaches a peak at Ellen's house party when the girls realize they all share a crush on Grant, who reciprocates Annie's feelings, culminating in a heartfelt kiss. Torn between her old relationship with Jason and her newfound affection for Grant, Annie experiences a whirlwind of emotions, especially after a shocking encounter reveals Jason's disloyalty.
Amid changing relationships, there are epiphanies for everyone; Ellen helps Michelle realize her feelings for Oliver, the principal's assistant, who shares her passion for history. As the girls set their sights on the prom, they eventually come to respect each other’s feelings, deciding to prioritize their friendships and call off the pact. As chaos breaks out at Stephanie's party, she and Emmett discover their mutual attraction through the haze of drama.
In the end, emotional resolutions are found as Kayla and Tim reconcile, while Michelle and Oliver start their own romance. Jason’s interruption raises the stakes yet again, but ultimately, the girls are determined to make the most of their senior prom night. They rally together, supporting Annie in her quest to reunite with Grant, culminating in a poignant moment as they establish a intimate space under the stars where Annie can finally embrace her desires. As they all share memorable encounters, this senior year wraps up with laughter, love, and the unforgettable bonds of friendship.
