Plot

After the death of the family's patriarch, Toula attempts to locate her father's childhood friends in Greece for a family reunion.

In the wake of Gus Portokalos and Ian's father Rodney's passing a year ago, the Portokalos family is grappling with grief. Nikos "Nick" Portokalos (Louis Mandylor), now separated, returns home, displaying immature behavior. Athena (Stavroula Logothettis) and her husband Yiannis are caring for Maria (Lainie Kazan), who is battling dementia.

Fotoula "Toula" Portokalos-Miller (Nia Vardalos) and Ian (John Corbett), though happily married, are facing the challenges of parenthood as their daughter Paris (Elena Kampouris) struggles with the responsibility of college, this is completely unknown to them. Ian is now retired but the family keeps reminding him that he has been fired from his job. Maria doesn't recognize Toula at times and says that she cannot be her daughter as she remembers her daughter to be young and beautiful. Since Gus died, the family has been a bit scattered as there was no natural head of the family anymore.

Victory (Melina Kotselou), a distant relative and the mayor of Gus' hometown Vrisi, invites the family here for a supposed reunion. This is Toula's first time in Greece as her parents never went back once they came to America. On the flight, Aunt Voula (Andrea Martin) introduces her assistant Aristotle (Elias Kacavas), Paris' college-mate, and Toula reveals she's bringing Gus' journal, containing his life story, to give to his three childhood friends in Greece as promised. Voula had set up Aristotle and Paris on a date, which did not go well. Paris was shocked to see that Voula brought Aristotle along with her for the trip.

They arrive in Athens, where Victory greets them, and go sightseeing. Their cab is an old freight wagon, which is in a very rickety condition. Victory does not allow the wagon to stop at any of the famous sites and takes them straight to the village. Victory has mannerisms exactly like Voula. The village is itself a ferry ride away and perched on top of a mountain.

In the nearly abandoned Vrisi (there are no restaurants or hotels open), they find Gus' childhood home and meet Alexandra (Anthi Andreopoulou), Gus's old flame and her assistance Qamar. Alexandra is a tough old woman, but she takes the entire family to her home to feed them. There, Victory confesses there's no reunion, hoping the Portokaloses would revive the village. Victory invited all the people who moved away years ago in the hope that they would see how beautiful it is and decide to stay back. 6 people stay currently in the entire village. The Portokaloses are the only ones who responded to Victory's invitation.

The family are given the largest house in village to stay, as it is empty now. The house has only one bedroom, and the family makes themselves cozy and comfortable. At night, Victory secretly takes Aristotle and Paris to a dance club in the nearest town. Victory brings Qamar along, and Qamar's boyfriend Christos. Christos and Qamar reveal they are secretly betrothed.

The family goes to a nearby town the following day, where Toula searches for Gus's friends without success and gets drunk on ouzo. Nick searches for the village's oldest tree and Ian befriends a monk, who possesses information about everyone's activities in the village. Ian gifts some food items to the monk, which were given to him as a gift by his neighbors in the village. The monk thanked him and wrote something on a piece of paper for him in Greek. Meanwhile, Aristotle tries to communicate with Paris, who rebuffs his advances without explaining why.

At dinner, Toula and Ian meet Peter (Alexis Georgoulis), Alexandra's son by Gus, whom the latter never knew about, as well as his son Christos (Giannis Vasilottos), and Alexandra's assistant Qamar (Stephanie Nur). Peter owns an olive oil factory in the village where he produced cold pressed olive oil. Qamar and Christos plan to establish an organic farm in the village. Peter accepts Qamar into his family once he realizes that she and Christos are already together. Meanwhile, Victory is sure that the village will have a reunion over the coming weekend and spends the week decorating the village all by herself.

Afterwards, Toula informs her family about Peter, but struggles to locate Gus' friends. Fortunately, the monk gave Ian a list of those who left the village, pinpointing one who moved to Syros. Toula shares this with Nikki (Gia Carides) and Angelo (Joey Fatone), who head to Syros and return with them.

Meanwhile, Toula discovers Nick brought Gus's ashes to Greece, following his father's wish for them to be scattered by the oldest tree in Vrisi. Later that evening, the family learns about Christos and Qamar's engagement, coupled with the revelation of Paris being on academic probation. Peter and Alexandra express disapproval, prompting Ian to offer intervention for Paris. However, the younger generation rejects external interference, opting to address their issues independently.

The next day, Peter comes to terms with Christos and Qamar's relationship, with Alexandra eventually doing the same. Soon, Alexandra also blesses the union. Victory recognizes the potential of a wedding to revitalize the village and initiates plans. Soon the village is busy preparing for Qamar's wedding to Christos. Peter manages to uncover a mountain spring blocked by rocks and as it flows, it brings water to the village and to the olive fields downstream.

Toula and Ian receive encouragement to unwind and relish their vacation while the rest of the family collaborates in organizing the wedding, albeit with their assistance in the final stages.

In a joyous celebration, Qamar's family joins them for her wedding to Christos. Paris opens up about her split with Aristotle, citing struggles with independence, and they agree to take things slow, much to Aunt Voula's delight. Nikki and Angelo arrive with Gus' friends, and Toula presents them with his journal.

Nick asks Toula to be the head of the family now. Later, Toula, Nick, and Peter privately scatter Gus' ashes around the tree, and Victory's mayor-ship receives praise. Toula and Nick decide to bring Peter with them to America, now as part of the family. The siblings, on the way, engage in a playful dispute over who should now lead the family, each citing their actions during the journey.