Brooks Rattigan, a determined teenage boy, aspires to gain admission to Yale, much to the dismay of his father, Charlie Rattigan, who encourages him to accept a full scholarship offer from the University of Connecticut. In an effort to support his college dreams, Brooks juggles part-time work at a sub shop alongside his best friend, Murph, a talented programmer. However, financial challenges loom large.
Seizing an unexpected opportunity, Brooks begins to pose as the boyfriend of his wealthy classmate, Celia Lieberman, from Greenwich. As he navigates the world of superficial dating, he discovers he possesses a remarkable ability to charm, particularly when he sets his sights on the beautiful yet snobbish Shelby. To elevate Brooks' status, Celia deceives Shelby by claiming he hails from the affluent town of Darien instead of their working-class Bridgeport roots.
To enhance his dating venture, Murph develops an app that markets Brooks as a versatile plus-one for various occasions. When Celia reveals her crush on Franklin, they concoct a scheme to execute a faux breakup, believing it will allow them to pursue Shelby and Franklin without consequences. As Brooks gains popularity and business booms, he unintentionally alienates Murph, who feels sidelined and decides to end their collaboration.
Celia, hoping to help Brooks with his Yale ambitions, arranges an interview but grows upset when she finds out he has researched the Dean, feeling deceived by his dishonest persona. Brooks defends himself, arguing that it mirrors his actions with the app, claiming, > “It’s no different from what I’ve been doing.”
Over time, Celia acknowledges that Franklin may not be the right match for her, although she keeps this realization to herself. The duo's staged breakup leaves Celia hurt and frustrated, leading to an unexpected slap from her, which Brooks, naively thinking it's all part of the act, fails to comprehend.
Following their phony breakup, Shelby invites Brooks to her school's formal, where they struggle to connect and engage in meaningful conversation. There, he encounters Leah, a girl who utilized his app for dating practice, who expresses her gratitude in front of Shelby, who reacts with offense. In a moment of honesty, Brooks reveals his true background, explaining his need for financial support to attend Yale. Shelby, feeling betrayed, calls him a liar and walks away.
Searching for solace, Brooks turns to Celia, but she declines to dance with him, asserting she doesn’t want to be someone he turns to last. Returning home, Brooks engages in a heartfelt discussion with his father, who reminds him that everyone is on a journey of self-discovery and expresses pride in his son's personal evolution.
Ultimately, Brooks decides to embrace the University of Connecticut’s offer, rejecting the notion that he must alter his identity for Yale. He mends his friendship with Murph and meets with Celia to convey his thoughts in a heartfelt letter. In it, Brooks reflects on his previous aspirations of superficial success—driving flashy cars, attending elite schools, and dating the most beautiful girls—all of which led him to become a poor friend and an ungrateful son. He realizes his moments of authenticity and genuine connection were spent with Celia and expresses his desire to pursue a relationship with her.
Later, Celia visits Brooks to apologize for her earlier actions, and they venture to the sub shop transformed for an upbeat party, where Murph reveals his admission to UConn. Brooks and Celia reconcile, sealing their renewed bond with a kiss as Murph and the charming Tuna Melt join in the celebration. The four friends then dance joyously, bringing the film to a heartwarming conclusion.
