The film starts in a bar where a guy named Jeremy (Timothy Simons) is waiting for his date, a model-like blonde woman. Instead, he is met by con artist Penny Rust (Rebel Wilson). She pretends that the girl in the picture that Jeremy was waiting for is her sister who was too shy to meet him because she is ashamed of her small breasts, so Penny almost tricks Jeremy into giving her money for her "sister's" boob job. However, another guy that Penny swindled finds her in the bar with the cops, and she runs out of there, managing to hide among trash bags since her dress looks like one.Somewhere in France, a Danish man named Mathias (Casper Christensen) spots an American woman, Josephine Chesterfield (Anne Hathaway), sitting alone at a bar. He approaches her and hears her story about winning a lot of chips at the casino. Mathias offers to sell Josephine his mother's valuable bracelet, only for an Interpol officer, Brigitte Desjardins (Ingrid Oliver), to come by and say that Josephine is an international criminal and that she stole the chips from an old man. In reality, Brigitte and the old man, Albert (Nicholas Woodeson), are in cahoots with Josephine, who is really an English woman posing as a dim-witted American to try and con other men. She manages to swipe Mathias's bracelet and swap it with a fake.Josephine boards a train heading toward the French Riviera, where she spots Penny conning another guy by pretending that she is trying to come up with ransom money for her kidnapped sister. Josephine is impressed by how Penny makes the man buy her a bunch of food. The two then meet in another train car where Penny explains to Josephine that she exploits men who think women are too vulnerable or incapable of caring for themselves. Penny also mentions that she is traveling to the town of Beaumont-sur-Mer to con rich men, but since Josephine lives there and doesn't want competition, she tricks Penny into heading toward Port-au-Prince.After arriving in Beaumont-sur-Mer, Josephine sees that Penny made it there by tricking a guy named Gregor (John Hales). Josephine has Brigitte arrest Penny by having Gregor identify her while she uses his money to get some kind of water jet pack. While in prison, Josephine goes to Penny's cell and makes her think that Gregor is a member of the Russian mafia and that she will be killed on the outside. She forces Penny to fly back home, but on the plane, Penny is called to the bathroom to meet with Mathias, who tells her that Josephine is also a con artist and that she fooled her as well. Before Penny decides to fly back to meet Josephine, she and Mathias have sex in the bathroom.Penny makes it back to Josephine's home and requests that she teach her to be as good of a con artist as she is. Josephine agrees and shows Penny some of her tricks for fooling men, as well as other random tasks for self-defense. They start with a few practice targets, starting with a Southern tycoon named Howard Bacon (Dean Norris). Josephine gets him to propose marriage to her, on the condition that he meet her "sister". She then introduces Howard to Penny, who is made up to look like a repulsive hag. Howard leaves in disgust and leaves Josephine with the engagement ring. Later on, Josephine pays Brigitte and Albert their share, but not Penny. Dismayed, Penny leaves Josephine, while also suspecting her of being a notorious con artist named Medusa.Josephine attempts to con an old man, only for Penny to come in and ruin everything. The two then make a bet to see who will con a rich man first. They spot their mark, a young app creator named Thomas Westerburg (Alex Sharp), who is seemingly clumsy and gullible enough to fool.Josephine tries to catch Thomas at a table in the casino, but Penny comes in pretending to be blind and ends up getting Thomas's attention. The two sit together at another table where Penny tries to convince Thomas to cough up money for an operation for her eyes. Josephine sees that Penny is using her tricks, so she tries to use some of Penny's. Thomas appears to be a nice guy toward Penny, and he tells her how he wants to make improvements to his app in a way that his bosses may not approve of. He then goes to the bar to find a doctor that Penny made up, and Josephine assumes the role of said doctor so that he can try and get money out of him. He brings her back to the room to "meet" Penny, who is displeased to see her opponent there. Josephine puts her through some "tests" for her made-up condition, which is mostly meant to torture Penny.The ladies later end up at a nightclub with Thomas. Penny convinces a trio of women that she is blind and that Thomas is her ex who is now with her best friend, Josephine. Penny gets Thomas alone and finds out that Thomas doesn't own his company as she believed and that he is practically broke, but he would apparently be willing to pay the rest of his money for Penny's operation. Penny becomes endeared to Thomas and starts to fall for him, which also makes her feel guilty about conning him.Josephine finds Penny in her room, and Penny admits her feelings about Thomas to Josephine. Now that things have gotten personal, Josephine decides to make their bet interesting by seeing which one of them will win Thomas over first. Josephine leaves and also brings the three women from before to handle Penny for lying to them. She then goes to Thomas's room to try and seduce him, but he insists on keeping things professional for Penny's sake. However, before Josephine leaves, Thomas decides to turn the lights off.In the morning, Penny has to rip her hand off the wall since it was super-glued there. She runs to Thomas's room just before he leaves, and he tells her that she is the one good thing that happened to him there. As he leaves, she tries to stop him but slips and falls. Thomas goes to help her and sees that she is moving her eyes and is not blind, believing this to be the result of good medical treatment. The two then go to Thomas's private jet to say farewell. After it takes off, Josephine goes running after him yelling for the plane to stop. She explains to Penny that after the lights went out, Thomas showed her a PowerPoint presentation on his new app and then asked her to shower before taking her to bed, and then when she got out, all of her clothes and items were gone. Penny tells her that she gave Thomas back $500,000 that Josephine allegedly stole from him, only for Josephine to say that she gave him that much money to invest in his app, which means that Thomas ended up conning both women. He sends them a message revealing that he was Medusa.Sometime later, Penny is back near Josephine's home where she gives Penny some money for her hard work. They are then met by Thomas, who is giving a tour to a group of people. He approaches the ladies and says that he has made $6 million so far that year from his new app and he thanks them for it, before adding that the three of them would make a great team. Although they are annoyed, they agree to it, and Penny kisses Thomas.It is now Christmastime. A guy named Todd (Rob Delaney) has been conned by the women, who hide under a Christmas tree because their dresses match the decorations. They meet with Thomas and sail off on a motorboat.