In a restaurant in East Great Falls,
Michigan, Jim Levenstein hints to his girlfriend Michelle that he is about to propose, until his dad calls to inform him he left the ring at home. She misinterprets his hints and performs
fellatio on him under the table, as his dad arrives with the ring so they are publicly exposed. Despite the awkwardness, Michelle accepts Jim's proposal. Jim and Michelle exclude their acquaintance, the boorish and vulgar Steven Stifler, from the wedding plans, but he notices the celebration party while passing and insists on taking part, seeing an opportunity to have sex with the bridesmaids. Jim agrees to let Stifler join in exchange for teaching him to dance, so he can surprise Michelle. Stifler, Jim, and his friends Paul Finch and Kevin Myers, travel to Chicago to secure Michelle's dream wedding dress, and trace the designer to a gay bar. Stifler's insecurity around homosexuals annoys the patrons, but he wins them over during a dance off with a large gay man called Bear. Entertained, Bear offers to provide strippers for Jim's bachelor party, while the dress designer agrees to make Michelle's dress. Michelle's younger sister Cadence returns to Michigan for the wedding, after breaking up with her boyfriend because he would not take her virginity. Hoping to win Cadence over, Stifler acts refined and intelligent like Finch, while Finch acts like Stifler, and Cadence takes a liking to them both. Meanwhile, Jim begins to have doubts about marriage, worried that he has only ever really been with one woman. His father's awkward reassurances fail to convince Jim. Stifler, Finch, and Kevin break into Jim's parents house to surprise him with the bachelor party and Bear's strippers, unaware Jim is bringing Michelle's parents over for dinner. The boys conceal the party from Michelle's parents until her mother finds a stripped and bound Kevin in the closet. They convince her parents that it is an elaborate plot to impress them by portraying Jim as a hero who rescues Kevin. In
Grand Traverse County, Michigan, wedding preparations are underway, despite mishaps: when Jim's shaved pubic hair is sucked into a kitchen vent which destroys the wedding cake, his grandmother expresses dislike for Michelle not being Jewish, and Stifler accidentally feeds the wedding ring to a dog. Cadence admits she likes Stifler but questions if he is pretending to be different around her. After Cadence agrees to sleep with Stifler, he steals a bottle of champagne from the kitchen, inadvertently turning off the cold room and killing the wedding flowers within. Jim and Michelle demand he leaves, supported by Cadence, who has learned of his true personality and intentions. Feeling guilty, Stifler works through the night to convince the florist to put together new floral displays, and enlists the help of his high school football team players and Bear. Seeing the new display, Michelle and Jim forgive Stifler, and Cadence reconciles with him, seeing he does genuinely care about his friends, and agrees to have sex with him in a supply closet before the wedding. Stifler is delayed by Jim, who thanks him, Finch, and Kevin for their help and support over the years. Unaware that Cadence was also delayed, Stifler enters the dark closet and has sex with someone, revealed to be Jim's grandmother, who was put there by ushers because of her unlikable personality. Jim's grandmother becomes more pleasant afterward to the delight of Jim's dad and Michelle. Struggling to convey her feelings through her vows, Michelle asks Jim's dad for help. He explains that love is not just a feeling, but the actions they do for each other; she happily thanks and calls him dad. Michelle and Jim get married and share their first dance together, privately acknowledging their shared awkwardness and perversions that make them perfect for each other. Stifler dances with Cadence, while the rejected Finch sits alone until Stifler's mom arrives. Though agreeing they are over each other following their previous trysts, they both retire to her room. ==Cast==