The 56-year-old actor married the 35-year-old designer and model in March 2009, and two will become three when their little one arrives.
Bruce's rep told People the couple are: "overjoyed with this news and they look forward to welcoming this newest addition into their family."
His three children, Rumer, 23, Scout, 20, and Tallulah, 17 will become big sisters to Bruce's new baby.
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The actor's ex-wife, Demi is not in such a state of martial bliss following accusations about her hubby Ashton Kutcher's recent fling.
Let's hope some of Bruce's good mood can rub off on Demi.