NOTE: This spoiler was sent in by Nikki
The movie begins with Sophie singing I Have a Dream. She then mails letters to Sam Carmichael (Pierce Bronson), Bill Anderson (Stellan Skarsgard), & Harry Bright (Colin Firth). The next day she meets up with her two best friends and explains to them she mailed a wedding invitation to her father. She doesn’t know which of the three men her father is, but she found her mothers diary, detailing the summer she had flings with all three men. They all feel from the passages in the diary that Sam has to be Sophie’s father. However, Sam was engaged and had to return home for his wedding. After this, Sophie’s mother hooked up with Bill. Later on, the diary tells how her mother hooked up with Harry. Sophie feels she will know which man is her real father as soon as she sees him. She wants her real father to give her away at her wedding. They sing Honey, Honey.
Harry and Sam arrive at the boat landing to find the ferry has left them. They realize they are heading to the same wedding when Bill offers them a ride on his boat.
Sophie and her friends are preparing their dresses for the wedding when her fiancée, Sky, comes in saying it’s a waste. He didn’t want a big wedding, but wanted to save the money for them to travel the world.
Donna (Meryl Streep) greets the ferry with her two best friends Rosie (Julie Walters), a best selling cookbook writer, and Tanya (Christine Baranski) who has a collection of rich ex husbands. They talk about men who have come and gone in their lives. Donna says she’s grateful she can wake up in the morning with no man to answer to.
As the three men journey to the island, they talk about how they haven’t seen Donna in years and don’t really understand why they’ve been invited to the wedding.
Donna and Sophie run a hotel on an island. Sky and Sophie have done lots of research on the villa and hope, with the help of the internet, to turn the place to a lover’s retreat. However the place is falling apart and the money is running out. They sing Money, Money, Money.
Once they finish singing, the ground shakes and a crack forms in the courtyard.
The three men arrive and are greeted by Sophie, but she doesn’t get the feeling she hoped. Sophie hides them in the old goat house next to the villa. She learns she was named after Bill’s aunt Sophia. Sophia admits to the men that Donna knows nothing of their arrival and wants to surprise her at the wedding. Harry and Sam don’t want to stay, but Bill refuses to leave. She talks with the men, gaining a little insight, until they hear Donna enter the house. Sophie makes them promise to hide then bails out the window. However, Donna has heard the commotion and curiosity get the better of her. She sees the men and instantly remembers them how they were 20 years ago. As she scales the building to get a better look at the 3 she sings Mamma Mia. She falls through the roof and has an awkward meeting with the 3. They chalk it up to a serendipitous occurrence for the 3 of them to be there together. It is obvious there are still sparks between Donna and Sam.
Tanya flirts with a young bartender while Donna goes searching for Sophie. Donna’s friends find her sobbing and sing. The friends freshen Donna up, give her booze and anxiety meds. Donna confesses she always said Sophie’s father was Sam, but she really is not sure which of the 3 it is. The women run to the goat house to get a peek, but the men are gone. Donna feels that Sophie knowing that one of them is her father would be a bombshell. She doesn’t want Sophie thinking her mom is an irresponsible slut. Friends sing Dancing Queen to cheer Donna up.
Sophie sees the men leaving on Bill’s boat so she swims to them to beg them to stay. She takes a ride with them around the island and gets to know each of them a little. The men sing Our Last Summer as they tell her about the time they knew Donna.
Sophie leaves the boat and meets up with Sky, who is upset because he’s been looking for her all day. They sing Lay All Your Love on Me. This leads into Sophie’s bachelorette party. Here Sophie is treated to the reunion of Donna and the Dynamo’s singing Super Trouper. While they are performing, the three potential dads show up to join the fun. During the party, all three come to think they are Sophie’s dad and tell her they will walk her down the aisle. Sophie doesn’t know what to do now because she has to tell two of them they aren’t her dad. The party sings Gimme, Gimme, Gimme. Sky’s bachelor party is shown and the song goes to Voulez-Vous.
The next day Donna and Sophie are each freaking out about the dilemmas at hand. Rosie goes out to Bill’s boat to keep the men occupied. Bill and Harry have a conversation where each thinks the other knows they are Sophie’s dad. Rosie interrupts their conversation and is bewildered at the site of Bill’s naked butt.
Donna meets up with Sophie and questions her about problems between Sophie and Sky. Sophie is confused about the 3 potential dads, but Donna thinks Sophie is getting cold feet and wants to call off the wedding. Sophie tells her she loves Sky and doesn’t want children who don’t know who their father is. Donna continues with preparations for the wedding, but is confronted by Sam. This was their dream to have a villa on the island. Sam doesn’t feel Sophie should get married. Like Donna, he feels she’s too young and should get out and see the world. Sam sings SOS.
Tanya is in charge of taking care of Harry. They are on a paddleboat together when Harry asks what a real father would do for a daughter. Tanya tells him they would pay for the wedding. Harry jumps off the boat and swims ashore. The young bartender swims up to the boat. Turns out he slept with Tanya the night before and is smitten with her. Tanya sings Does Your Mother Know. In the meantime, Harry approaches Donna and presents her with a check for the wedding. She tries to give it back, but Harry runs away.
Sophie goes to Sky and says she needs his help. She explains the 3-dad situation and it upsets Sky. She didn’t tell him about it and he feels the big wedding is nothing more than a ploy to find her dad. She feels knowing her dad will help her find herself. Sky explains he found who he was in her. Sky leaves and Sam approaches Sophie. He explains that just having a big white wedding won’t make her happy if she’s not ready for marriage.
Sophie goes to Donna and asks her to help prepare her for the wedding. Donna sings Slipping Through My Fingers. Sophie tells her she is a great person for doing all she’s done, raising a daughter alone, running the villa, etc. Donna says she wouldn’t have it any other way.
Sam runs to talk to Donna before the wedding. Donna says she’ll give Sophie away. Sam begs her to talk about the past and what they still feel. Donna sings The Winner Takes It All. Donna gets to the wedding and walks Sophie down the aisle. The wedding begins but Donna stops it to explain to Sophie and everyone else she doesn’t know which man is her dad. Donna realizes that Sophie sent for the men and that’s why they are there. Donna asks Sophie to forgive her. Sophie says she loves her even if she’s slept with 100 men. Sam steps up and confronts Donna. Turns out when he left Donna 20 years ago, he loved her so much he came back, but Donna was on a date with Bill. That’s when Sam went back and married his fiancée. Harry steps up and says that he wants to be a third of Sophie’s dad. Turns out that Donna was the first and last woman Harry ever loved. He’s gay and Sophie is his only real chance for a child. Bill steps up and says he wants to be a third of her dad as well. Sam tells Sophie, she can find out which of them is her real father, or accept all three of them as her father.
Sophie loves this and tells Sky she doesn’t want to get married. They want to travel and see the world together before they decide to marry. Sam then asks Donna to marry him. He’s loved her for 20 years and he’s tried to tell her he still loves her from the time he stepped back on the island. They sing When All Is Said And Done.
Bill says it all worked out for the best because he is a lone wolf. Rosie turns to him and begins singing Take a Chance On Me. He tries to escape but then relents and takes her in his arms.
The wedding party is dancing and singing in the courtyard when water comes spraying up through the crack in the courtyard. They all dance around kissing and singing Mamma Mia.
The movie ends with Sophie once again singing I Have a Dream as she and Sky set sail and leave the island.