The baby, a boy, will join 13-month-old big brother Axel Lee. The couple married in 2008.
"We're having a boy! We're so happy that Axel gets to have a brother so close in age. And that I get to add another set of balls to my very, very male world," the actress, 36, joked to PEOPLE.
(image via: http://celebritybabies.people.com)