The musician has admitted he feels "blessed" with the knowledge he's going to be a dad.
Posting a photo of him with his wife, who is holding her stomach, on Instagram he announced: "Izzy and I are so happy and feel truly blessed to be able to share with you that we are expecting our very own little miracle #BabyJudd @izzyintheattic"
Harry and Izzy - who was the violinist in classical group Escala - met when she performed as part of the string section on McFly's 2005 tour.
The couple got engaged in May 2012 during a romantic getaway in St. Lucia and they got married in December that same year.
Harry recently admitted having bandmate Tom Fletcher's son Buzz on tour with McBusted had made him broody to start a family of his own.
The sticksman said: "We rarely see Buzz cry or make a fuss, he's always laughing. He's so cute it's frightening."
Story: ©BANG Showbiz.