Plot

A young man must defeat his new girlfriend's seven evil exes, who are willing to do anything to prevent her happiness with someone else.

Scott Pilgrim plays in a band which aspires to success. He dates Knives Chau, a high-school girl five years younger, and he hasn't recovered from being dumped by his former girlfriend, now a success with her own band. When Scott falls for Ramona Flowers, he has trouble breaking up with Knives and tries to romance Ramona. As if juggling two women wasn't enough, Ramona comes with baggage: seven ex-lovers, with each of whom Scott must do battle to the death in order to win Ramona.—Jim Beaver <jumblejim@prodigy.net>

Scott Pilgrim (Michael Cera) is an unemployed 23-year-old bass guitarist in an up-and-coming garage rock band who is dating a cute 17-year-old high school girl, Knives Chau (Ellen Wong). He is having fun in life and rolling along at a nice even tempo until one day Ramona Flowers (Mary Elizabeth Winstead) roller-blades into his life. Ramona moved to Toronto from New York City to find peace and quiet and leave her past behind. No one knows what her past is, but Scott will find out very soon as he tries to make Ramona his new girlfriend. Before Scott can begin dating Ramona, he must prove himself by defeating the league of her seven exes who controls her love life. They will do anything to get rid of and destroy any new boyfriend Ramona may consider. If Scott wants to find true love with Ramona, he must defeat all seven, before the game is over.—Douglas Young (the-movie-guy)

In Toronto, Scott Pilgrim (Michael Cera), a 22 year old bass guitarist for the band "Sex Bob-Omb", begins dating a 17-year-old high-school student Knives Chau (Ellen Wong), much to the disapproval of his friends 22 years old Stephen Stills (Mark Webber), 23 years old Kim Pine (Alison Pill), 20 years old "Young" Neil Nordegraf (Johnny Simmons), his roommate 25 years old Wallace Wells (Kieran Culkin), and his younger 18 years old sister Stacey Pilgrim (Anna Kendrick). Knives and Scott haven't even kissed each other yet and were far from having sex. They held hands together once and Knives got embarrassed.

It's been a year since Scott was dumped by Natalie. Wallace is gay and is dating Other Scott (Ben Lewis). Everyone is worried that Scott is now dating a high-school student. Julie Powers (Aubrey Plaza) is a 23-year-old worker at a record store. Scott imagines his life to be like a video-game, with every character having their title cards, displaying essential information along with their powers.

Scott meets an American girl, Ramona Flowers (Mary Elizabeth Winstead), an American Amazon delivery girl, who has been appearing in his dreams, and becomes obsessed with her. Julie tells Scott that Ramona is out of his league. She is the coolest girl in town, has a boyfriend in New York, but had a big fight with him recently. Julie says that Ramona keeps mentioning a name Gideon. Scott loses interest in Knives but does not break up with her before pursuing Ramona. Both Wallace and Stacey tell Scott to break up with Knives before going after Ramona, but he ignores them.

Scott orders stuff from Amazon so Ramona has to come and deliver it. Scott asks Ramona out on a date, and she accepts else otherwise Scott would not sign for the package. They end up in Ramona's apartment due to a snowstorm and Scott sleeps in her bed, though Ramona changes her mind about having sex with Scott on their first date. Scott invites Ramona to the Battle of the Bands. Scott also receives an email from Matthew Patel challenging him to a duel.

While playing in a battle of the bands sponsored by one "G-Man Graves" for a record deal, Scott is attacked by Matthew Patel (Satya Bhabha), who introduces himself as the first of Ramona's "evil exes". Ramona & Patel dated for a week and a half in 7th grade, post which Ramona dumped him. Scott defeats Patel and learns from Ramona that, in order for them to date, he must defeat all seven of her evil exes. Ramona and Knives were both at the Battle of the Bands and Knives kisses Scott in front of Ramona. While going home with Scott on the bus, Ramona admits that she is dating Scott and agrees to make out with him.

The next day, Knives invites Scott to her birthday dinner with her parents. Knives says that she is in love with Scott. Scott finally breaks up with Knives, who blames Ramona and swears to win him back, by becoming more like Ramona. Scott battles Ramona's second evil ex, popular actor and skateboarder Lucas Lee (Chris Evans), who he defeats by tricking him into performing a dangerous skateboard grind that causes him to ignite.

Scott later encounters the third evil ex, Todd Ingram (Brandon Routh), who is dating Scott's ex-girlfriend, Natalie "Envy" Adams (Brie Larson). Envy is in a band herself and invites Scott's band to open the show for them. Todd is part of Envy's band. Todd initially overpowers Scott using his psychic vegan abilities but is stripped of his powers by the Vegan Police after Scott tricks him into drinking coffee with half and half cream, allowing Scott to defeat him.

Scott begins to grow upset with Ramona over her dating history by the defeat of the fourth ex, Roxanne "Roxy" Richter (Mae Whitman). Ramona had a brief lesbian fling with Roxy before she dumped her & made her an "evil ex". When Roxy attacks Scott, Ramona steps in to protect Scott and defeat Roxy. Scott grows frustrated during the process, and after an outburst regarding Ramona's dating history, she breaks up with him.

During the second round of the battle of the bands, Sex Bob-Omb faces off against the fifth and sixth evil exes, twin Katayanagi brothers Kyle (Shota Saito) and Ken (Keita Saito), earning Scott an extra life upon their defeat.

During the battle, Scott sees Ramona together with her seventh evil ex, Gideon Graves (Jason Schwartzman), who turns out to be Sex Bob-Omb's sponsor, G-Man. The members of Sex Bob-Omb accept Gideon's record deal, except for Scott, who leaves the band.

Upon returning home, Scott receives a phone call invitation from Gideon to his newly opened Chaos Theater where Sex Bob-Omb is playing, claiming there to be "no hard feelings". Scott arrives and challenges Gideon to a fight, professing his love for Ramona and gaining a sword called the "Power of Love", which Gideon easily destroys. Knives then crashes the scene to fight Ramona over Scott. Scott goes to break up the girls' fight, only to accidentally reveal that he cheated on them with each other before he is killed by Gideon.

Ramona visits Scott in Limbo and apologizes for getting him involved in her affairs, revealing that Gideon had planted a mind control device in the back of her head. Scott realizes he still has an extra life and uses it to return to life at the moment in time when Gideon first called him. Scott reenters the Chaos Theater where he makes peace with his friends and challenges Gideon again, stating he is fighting for himself and gaining the much stronger "Power of Self-Respect" sword with which he strikes down Gideon.

He then apologizes to Ramona and Knives for cheating on them, but Gideon interferes and knocks down Ramona, leading Scott and Knives to team up and defeat him. Free from Gideon's control, Ramona prepares to leave, but Knives accepts that her relationship with Scott is over and encourages him to follow Ramona. He does, and the two start their relationship anew.