The couple are also the parents of 13-month-old Harlow.
"What's better than winning an Oscar? I am so happy to tell everyone that Harlow is going to be a big sister! God has truly blessed my family. Hope you're all feeling as good as I am right now," Madden wrote on the Good Charlotte Web site.
He didn't say when the baby is due or what its sex is.
Richie is the socialite daughter of singer Lionel Richie and the former co-star of the reality television series "The Simple Life."
Celebrity Breakups and divorces of 2014 [PHOTOS]