Successful and single 29-year-old Beth, an art curator at the Guggenheim, is at a point in her life where love seems like a luxury she can't afford. Waiting for the "perfect" romance has embittered her. After flying to Rome to be the maid of honor in her younger sister Joan's impulsive wedding, she meets 27-year-old Nicholas Beamon, the best man. He rescues her in a couple of difficult situations but they are both clumsy. Still, they hit it off.

As Beth comes to believe in love again, she sees Nick kissing another woman, who turns out to be the groom's "crazy cousin." Slightly drunk and jealous at seeing Nick with another woman, she picks up coins (a poker chip, a rare coin, a penny, a trick quarter and a Euro) from the "fountain of love" (based on the Trevi Fountain). Joan tells her that legend says if you take coins from the fountain, the owner of the coin will fall in love with you.

Beth is pursued back in New York City by a band of pushy suitors whose coins she gathered, including a diminutive sausage magnate Al, lanky street illusionist Lance, a doting painter Antonio, and a narcissistic male model Gale. She must return the coins to the fountain to break the spell. As she falls in love with Nick, she realizes that the poker chip belongs to him and is convinced that he is under a spell, not truly in love with her.

Joan calls Beth on the day of a gala and tells her that the spell can also be broken by returning the coins to the original owner. Stacey, Beth's secretary, concerned about her, overhears the conversation and steals the coins. She believes that Beth would lead a better life with people loving her, regardless of the spell.

When Beth's suitors all show up together at her apartment, she tells them she does not love them and plans to return their coins. She also tells them of her love for Nick, but realizes that Stacey has stolen the coins. She sets off to retrieve the coins, aided by her suitors. All pile into a yellow Vespa 400 microcar, which careens through city traffic, into the Guggenheim and up an elevator.

Stacey returns the coins and Beth gives them back to their respective owners. Left with the poker chip, she calls Nick and thanks him for making her believe in love again. Nick makes his way to the gala to search for Beth in a sudden lightning storm that hits New York. There he happens to pick up his poker chip, dropped by Beth, and convinces her his love was true.

On Beth and Nick's wedding day in Rome, Lance tells her he had several poker chips, and Nick did not break out of the spell. While exchanging wedding vows, Beth hesitates and dashes out of the church. She revisits the fountain and wades in again. Nick appears and joins her in the fountain. He said he had never thrown a chip in. He drops a poker chip in the water, and the priest is heard yelling, "Free of temptation!" Beth finally believes Nick and kisses him.