Returning cast members will be in the modern scenes while new actors will be found to play their younger versions, each singing more ABBA.
The project is being described as a sequel-prequel hybrid, with scenes taking place in both present day and in flashbacks.
According to The Hollywood Reporter, Universal is making a move on a sequel to Mammia Mia!, a successful 2008 musical that was based on a Broadway musical of the same name.
The original film followed the story of a girl (Amanda Seyfried) who invites three men to her wedding in hopes of learning which one is her father.