The proud daddy took to Twitter last night to reveal the family's exciting news to fans and followers.
The 41-year-old Take That star and X-Factor judge wrote: "My wife and I are expecting our 4th child #Anotherowngoal."
He then went on to joke that he had his eye on Peter Andre's 'Celebrity Dad of the Year' crown, tweeting:"Celebrity Dad of the Year #moveasideandre!"
Gary and Dawn married in 2000, and are already proud parents to Daniel, 11, Emily, nine, and Daisy, three.
The chuffed dad-to-be thanked his 1.3 million Twitter followers for their congratulations, saying: "What a lovely bunch you are. Thank you for all your kind messages.We are a very excited family."
Aw, what lovely news, and another celeb baby on the way!
The question is, will Barlow Jnr join his or her dad for the X-Factor auditions later this year, like baby Hollie Rose did for BGT?