Scott Pilgrim, played by Michael Cera, is a 23-year-old bassist for the indie garage band Sex Bob-Omb in Toronto. He begins dating Knives Chau, a 17-year-old high-school student, despite the disapproval of his bandmates, his roommate Wallace Wells, and his younger sister Stacey Pilgrim. The story kicks off with a chance meeting at a party where he first catches a glimpse of Ramona Flowers, an American delivery girl, whom he had already seen in a dream. While he feels a pull toward Ramona, Scott gradually shifts his attention away from Knives, yet he hesitates to end things right away before pursuing the mysterious new love interest.
The plot accelerates during a battle of the bands sponsored by Gideon Graves, a powerful record executive. Scott faces a brutal confrontation when Ramona’s ex-boyfriend Matthew Patel attacks him, but Scott overpowers Patel. As the contest unfolds, Sex Bob-Omb’s rivals are dramatically dismantled, and Scott receives a crucial revelation: to date Ramona, he must defeat her remaining six evil exes. This prophecy sets Scott on a comic-book-style quest through a series of escalating duels.
Scott finally ends things with Knives, who blames Ramona and vows to win him back by trying to imitate her. His next challenge is Lucas Lee, Ramona’s second ex, a famous actor and skateboard enthusiast. Scott defeats Lucas by exploiting an icy railing in a clever trick, proving that brute force isn’t enough to win Ramona’s heart. The band earns an opportunity to open for the band Clash at Demonhead, bringing them into the orbit of Ramona’s third ex, Todd Ingram, a vegan bassist dating Scott’s ex, Envy Adams, the lead singer. In a bid to level the playing field, Scott deceives Todd into drinking half-and-half, which leads to an encounter with the vegan police that strips Todd of his powers, allowing Scott to land a decisive blow.
The journey continues with Ramona’s fourth ex, the bisexual ninja Roxy Richter, where Scott, with Ramona’s help, fights and defeats her. Yet tensions simmer beneath the surface as Ramona’s dating history becomes a source of jealousy and frustration for Scott, culminating in Ramona breaking up with him and leaving behind a list of her exes. At the next battle of the bands, Sex Bob-Omb vanquishes Ramona’s fifth and sixth exes, the techno twins Kyle and Ken Katayanagi, earning Scott an extra life and inching closer to his ultimate goal.
Despite this, Ramona seems to reunite with her seventh ex, Gideon Graves. The band agrees to Gideon’s record deal, except for Scott, who resigns in protest, which prompts Young Neil to step up as the new bassist. Gideon invites Scott to perform at his Chaos Theater, where a final duel for Ramona’s affections unfolds and Scott wields the legendary Power of Love sword. Just as Ramona is attacked by Knives, Scott is forced to reveal that he has cheated on both women, a revelation that Gideon uses to seize the moment and kill Scott. Ramona visits him in limbo and reveals that Gideon has implanted a mind-control device in her, leaving Scott in a perilous state.
A lucky 1-up brings Scott back to life, and he returns to Chaos Theatre to reclaim his agency. He reconciles with his friends and faces Gideon again, this time for himself, wielding the Power of Self-Respect sword. After apologizing to Ramona and Knives for his infidelity and accepting his own flaws, Scott teams up with Knives to defeat Gideon. With Gideon defeated and Ramona free from control, she prepares to leave, signaling a possible future apart from the past.
In a final twist, Scott encounters a darker reflection of himself, Nega-Scott, and the two discover an odd camaraderie in their shared shadows. Knives watches as Scott and Ramona’s relationship takes a new turn, and at her urging, Scott leaves with Ramona to “try again,” leaving behind the old patterns and stepping into an uncertain but hopeful future.
