Nia Vardalos, who wrote and starred in the film, will reprise her role as the first-generation Greek-American woman while John Corbett will return as the non-Greek man, who falls for her.
Rita Wilson, Tom Hanks and Gary Goetzman are returning as producers.
The story of the film began as a play from Vardalos that told of her life growing up in a Greek household in Winnipeg and then marrying a non-Greek.
Wilson, who is half-Greek, saw the play and brought it to the attention of Hanks.
The original film was directed by Joel Zwick but the producers are yet to announce a director for the sequel, which involves the reveal of a family secret and a new wedding, described as bigger and fatter, that brings the clan together again.