On a picturesque Greek island, Sophie, a young woman about to be married, dreams of having her father walk her down the aisle. However, she has never met him and her mother, Donna, an independent and spirited former singer, refuses to talk about the past. Sophie uncovers her mother’s old diary and finds entries which intimate at three potential fathers: Sam, Bill, and Harry. Without informing her mother, Sophie secretly invites all three men to her wedding, believing that she will be able to recognize her father on sight.

As the wedding draws near, the three men arrive on the island, unaware of Sophie’s true motives for the invitation. Their presence causes a series of comedic and touching encounters, as old flames are rekindled and secrets come to the surface. Meanwhile, Donna, reunited with her former bandmates, the Dynamos, goes through her own emotional journey upon seeing her past loves again. The island's vibrant life, music, and dance embolden the characters as they navigate this unexpected reunion and the complexities of their shared histories just as the festivities begin.