The 38-year-old entertainer is expecting her first child with boyfriend actor Steve Kazee. Dewan has a daughter, 6-year-old Everly, with her ex-husband, Channing Tatum, who she split from back in April 2018 after nearly nine years of marriage. This will be 43-year-old Kazee's first child.
Dewan shared the happy news on Instagram, posting a picture of herself cuddling with Everly, with her baby bump on full display.
"Becoming a mother is quite simply the absolute best most incredible thing that has ever happened to me ?," she captioned the pic.
"@stevekazee you are a gift from above and i couldn’t be more excited to be expanding our family together...! Thank you guys for all the love!!"
Kazee also shared the happy news with a sweet post of his own, writing, "Well...the news is out. I can’t even begin to describe the feelings that I have had since we first learned that Jenna was pregnant! I have waited my entire life for this moment and couldn’t have found a better person to build a family with."
"The past year and a half has brought so many things into my life that have filled me with the deepest of gratitude. A partner who radiates love, warmth, and kindness. A partner who has faced some of the hardest moments life can deal you with grace, humility, and a desire to learn from the ups and downs. A partner who is continuously growing from those lessons and who supports my growth as a person with love, unwavering support, and understanding," he continued. "Jenna also brought with her one of the greatest gifts one could ever imagine...her beautiful daughter. Evie burst into my life like a supernova and has continued to burn so brightly in it. I have learned so much about parenting already from watching how amazing Jenna is with her and Evie has taught me so much about what it means to love and communicate with a child and I can’t wait to give her a sibling and make our little family a little bit bigger."
When ET caught up with Kazee in December, he said that he was "very happy" during the holiday season.
"I'm very happy at the moment, it's a good holiday right now. It's a good Christmas this year," he said. "You know, it's a very good holiday this year. I've had my birthday -- Oct. 30 -- so I get sort of Halloween, Thanksgiving, Christmas, it's been perfect this year and that's all I can say."
As for Dewan telling ET that she was "very happy" back in November, Kazee insisted that "she's a very happy person in general, I think... I can't take any credit."
Watch the video below for more on the happy couple.