Willis, 59, and model Emma Heming-Willis, 35, welcomed their second baby girl together on Monday, his rep confirmed to People.
They're already parents to 2-year-old Mabel Ray and named their newest addition Evelyn Penn Willis. The little one weighed in at 8 pounds and 10 ounces, the mag said.
"Both mother and baby are healthy and doing beautifully," his rep said in a statement. "Mabel is delighted to have a new baby sister."
Willis married Heming in 2009, and the couple celebrated their fifth wedding anniversary in March.
The "Red 2" star also has his hands full with a number of movies lined up: "Sin City: A Dame to Kill For" is set for August release and also stars Jessica Alba, Mickey Rourke, Ray Liotta, Josh Brolin and Joseph Gordon-Levitt. Willis will also appear in "The Prince" this year with John Cusack and 50 Cent.