Heigl gave birth to a son named Joshua Bishop Kelley Jr. on 20 December, PEOPLE confirmed.
The couple haven’t released any further details.
When announcing they were expecting their third child in June 2016, the couple said their daughters were thrilled to be getting a baby brother.
“Josh and I are overflowing with joy and gratitude,” she told PEOPLE at the time.
“This is an incredibly exciting time for us filled with hope, anticipation and hormones.”
Heigl opened up about her experiences becoming a first time biological mother on her blog, shortly after announcing her pregnancy.
“We were considering adoption again, fostering, or pregnancy if possible,” she wrote.
“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!”