The "Vampire Diaries" star took to Instagram to announce the news while posting a photo of himself kissing his wife's belly.
"To our friends, family, and rest of the world. In my 38 years on this earth I've never experienced anything more powerful and beautiful than this. I can't think of anything more exciting than this next chapter and we wanted you to hear this from us first," he wrote.
"This has been the most special time of our lives and we wanted to keep it between the three of us for as long as possible so we could enjoy this time with each other and our little one who is growing so fast…because that's what they do, they grow so fast," he continued. "Thank you for your kind energy. Love, Ian."
It's the first child for the loved-up couple, who recently celebrated their two-year anniversary.
The "Twilight" star also shared the photo of herself with her hubby on Instagram.
"Hi Little One. I know you, but only because I feel you," she wrote to her unborn child. "How is it possible to love someone so much already? All I know for sure is it's the strongest feeling I've ever felt. We've been sharing this body for quite some time, and we've already experienced so much together. We can't wait to meet you… Love, Your parents."