Mattias Ferrell was born in the early hours on Saturday in Los Angeles, according to a statement from his publicist Matt Labov.
“All are healthy, happy and otherwise okay,” Labov said.
Ferrell and his wife Viveca have one other boy, 2 year-old Magnus.
The Old School star made the announcement on Thursday night while appearing on The Tonight Show With Jay Leno.
Ferrell told the talk show host, “My wife is pregnant again.”
When asked by Leno if he is indeed the father, Ferrell joked, “I’m not the father. Chuck Norris is the dad – we’re so excited about that.”
Ferrell, 39, and Paulin, 37, wed in 2000 and have a two-year-old son, Magnus.
The expectant parents have been trying to prepare Magnus for the new arrival.
Ferrell added, “We’ve been trying to tell him, ‘Mommy has a baby in her belly’. Then one day he was like, ‘Mommy has a baby in her head!’
“My wife does have an abnormally large head. It’s grotesque…but I said, ‘No, no she doesn’t'… and we had a laugh.”