The actress announced via Twitter that she and husband James Thornton are expecting a third child to add to daughter Eva, three, and one-year-old son Kit.
Joanna tweeted: "Some good news! We've got baby number 3 on the way!!!! Morning sickness is a breeze when you're already looking after a 3 and 1 year old!"
James added: "Great news! Baby number 3 is on the way! Gonna be shifting from man to man marking to more of a zonal system of child control!"
Joanna, 38, is best known for her role as Stacey Shipman in the hit comedy series Gavin & Stacey. She's also appeared in Love Actually, Doctor Who, From Hell and Nativity 2: Danger In The Manger.
James, 40, is best known for his role of John Barton in Emmerdale.
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