Act One

On a small Greek island, we meet Sophie as she sends off three envelopes in the mail ("Overture/Prologue"). She announces the names of the men they're addressed to - Sam Carmichael, Bill Austin, Harry Bright. Lisa and Ali, Sophie's friends, arrive and reveal that Sophie's wedding is tomorrow. Sophie confesses to them that she's invited her father to the wedding…or at least the three men who could possibly be her father. After going through her mother's diary from the year she got pregnant ("Honey, Honey"), Sophie has determined that Sam, Bill, and Harry are the candidates to walk her down the aisle.

Donna, Sophie's mother, greets her lifelong friends Tanya and Rosie, who have just showed up for the wedding. The trio used to perform as the group Donna and The Dynamos. Running the Taverna, an inn on the island, Donna laments constantly working ("Money, Money, Money").

Sam, Harry, and Bill arrive at the Taverna. Sophie greets them, shocked to see them all there. Spotting his old guitar, Harry begins to strum a tune and Sophie joins him ("Thank You For The Music"). Sophie admits to them that she was the one who sent the invitations. Sam is clearly distressed by this. Just as Sophie is about to take them to their rooms, Donna comes out and sees them all there. Once she sees Sam, she is overcome with mixed emotions ("Mamma Mia").

Rosie and Tanya try to console Donna ("Chiquitita"). Donna tells them that although she always told them that Sam was Sophie's father, she wasn't really sure. She also tells them that Sam and the two other men who might be the father are at the Taverna. Rosie and Tanya rouse Donna's spirits, telling her that the Donna who used to be the life of the party is still inside her ("Dancing Queen").

Sophie asks Sky, her fiancé, to promise her he will never leave her like her father left Donna. Sky promises his constant love to her ("Lay All Your Love On Me") before Eddie and other friends lead him off for his stag night.

At Sophie's "hen night" (bachelorette party), Donna, Tanya, and Rosie perform in their old costumes as Donna and The Dynamos ("Super Trouper"). Sam, Bill, and Harry show up, and Sophie lets them join the fun ("Gimme, Gimme, Gimme"). Sophie gets a moment alone with Sam, who asks her why she's invited him to the wedding. Sophie, unable to tell him the truth, dances with Harry and tells him she does not know who her dad is. Before he can respond, Harry is whisked away by dancers. Bill gets to dance with Sophie, who tells him that his great-aunt Sophia was the one who left Donna the money for the Taverna in her will. Once Bill learns how old Sophie is, he has an epiphany, but Sophie is taken away by the party dancers before either can say anything else.

Bill and Sophie have another moment alone. Bill tells Sophie to come clean to Donna about trying to find her father. Sophie tells him she's tired of secrecy ("The Name Of The Game"). She asks him to give her away at the wedding and to let it be a surprise for Donna. Bill agrees.

Sky and his stag party return and join Sophie's bachelorette festivities ("Voulez Vous"). Sam takes Sophie aside and declares that he will give her away, clearly convinced he's her father. Before Sophie can object, they are swept up in the dancing. Harry then takes Sophie aside and claims that he will be the one to give her away. Overwhelmed, Sophie breaks away from the dance in a state of shock.

Act Two

After the "Entr'acte" plays, the curtain comes up on Sophie having a nightmare about her anxiety over her three prospective fathers and wakes up in distress ("Under Attack").

Donna thinks Sophie is upset because she secretly wants to call the wedding off. Sophie fires back that she would never want to raise a child without a father figure and storms off. Donna is left alone, feeling hurt and full of regrets ("One of Us"). Sam approaches Donna, and they look back on how things used to be between them ("SOS").

Pepper, one of Sky's friends, approaches Tanya on the beach and tries to flirt with her. Tanya chides him and tells him off ("Does Your Mother Know?"). Sophie finds Sky and confesses to him about her plan to bring Sam, Bill, and Harry to the wedding. Sky accuses her of using their wedding as a ploy to find her father and walks off. Sophie tries to go after him, but Sam stops her. Sam explains to Sophie that he left Donna to get married and have kids, only to end up divorced and remorseful for settling down too young ("Knowing Me, Knowing You"). Sophie, convinced that her love for Sky is stronger, leaves him to find Sky.

Harry finds Donna and offers her a check to help pay for the wedding. They reminisce about their time together years ago ("Our Last Summer"). Sophie enters with her wedding dress and asks Donna to help her get ready. Donna gets her daughter in her wedding dress, seeing her little girl all grown up ("Slipping Through My Fingers"). Sophie asks Donna to be the one to give her away. After Sophie leaves, Sam comes in and tells Donna he should walk Sophie down the aisle. Donna refuses to hear it and tell him he's done enough to her ("The Winner Takes It All").

Bill comes to Rosie and tells her of his anxiety over marriage and children, having sworn a life of adventure. Seeing a kindred spirit, Rosie woos him ("Take A Chance On Me"). Bill is about to succumb when guests arrive for the wedding.

Donna walks Sophie down the aisle. As the ceremony is about to start, Donna announces that Sophie's father is present but doesn't know which man he is. Sam, Bill, and Harry are bewildered. Harry says he is overjoyed to be one of Sophie's three dads and admits to Donna that he is now in a committed relationship with a man back home. Sophie proposes to Sky that they not get married and instead go see the world. With a priest still present, Sam proposes to Donna, who accepts ("I Do, I Do, I Do"). There ends up being a wedding after all!

The show ends with Sky and Sophie leaving the island to go on a new adventure together ("I Have A Dream").

The company takes their bows along to some audience-rousing hits ("Mamma Mia", "Dancing Queen", "Waterloo").