This marks Heigl's first pregnancy, and her and Josh Kelley's third child together.
Katherine Heigl and husband Josh Kelley are about to be a family of five.
The 37-year-old actress is pregnant, Kelley excitedly confirmed on Instagram on Thursday.
"Well I guess the cat's out the bag!!!!" Kelley wrote. "We're so excited people!!! What an awesome journey!!! Can't wait to hold this little nugget."
The couple tells People that they're expecting a baby boy in January. Heigl and Kelley, 36, are already parents to 7-year-old Naleigh Moon and 4-year-old Adelaide Marie Hope.
"This is an incredibly exciting time for us filled with hope, anticipation, and hormones," Heigl joked to the magazine. "Well, only I'm filled with hormones, but everyone in the family gets to enjoy them."
Heigl shared a picture of her ultrasound on Instagram. In a new blog post, she revealed that her and her hubby were definitely planning on expanding their family.
"We've known for awhile that we wanted to add to our family and frankly didn’t really care how we chose to do that," she wrote. "We were considering adoption again, fostering, or pregnancy if possible. Seeing as I have never been pregnant and as my OB/GYN reminded me last year, I'm of advanced maternal age, I wasn't sure pregnancy was even in the cards for us. Turns out it was very much in the cards!"
This marks the former Grey's Anatomy star's first pregnancy. The couple adopted daughter Naleigh, who was born with a congenital heart problem, from South Korea in September 2009 when she was nine months old. They adopted their second child, Adelaide, domestically in 2012.
Heigl and Kelley, a musician, have been married since December 2007.
WATCH: Katherine Heigl Sings (For Real!) in an Exclusive Clip of 'Jackie & Ryan'
ET chatted exclusively with the pair on the set of Kelley's music video for "It's Your Move" in March, which Heigl both directed and starred in. Kelley got candid about hitting a rough patch in their marriage, which inspired the song.
"I think it was a year or two after we first got married, we got into our first real big fight. One of those, like, really, really serious fights," Kelley explained.
Though clearly, the two were able to work it out.
"We live a very normal, simple life. I love being a dad, I love being a husband," Kelley gushed. "It's just one dude and a ton of chicks!"
... Looks like that will be changing come January!
Watch our candid interview with the couple below:
