Ladin shared on Twitter that Katy gave birth to a baby boy named Maxwell David on Friday (December 21).
"Wow! The last 24 hrs have been the best of my life. Forever changed, I am now a father. Maxfield David Ladin," the actor wrote.
He added over the weekend: "2 days old, but never too young to start watching football. #Texans. Katy & I are loving all the well wishes. Thank You!! We are #BEYOND excited."
Ladin announced that his wife was expecting the couple's first child in May, saying at the time: "Katy and I couldn't be happier, we have always wanted to be parents."
His series The Killing has been picked up for a third season as part of a co-production between AMC and Netflix, but the series will undergo a cast overhaul.