The How To Train Your Dragon funnyman, who also hosts U.S. TV's The Late Late Show, broke the news to fans on his Twitter.com page on Wednesday (14Jul10).
He wrote, "Holy crackers! Mrs F is pregnant. How did that happen? Oh yeah I know how. Another Ferguson arrives in 2011. The world trembles."
Ferguson, 48, is already a dad to nine-year-old Milo Hamish, his son from his second marriage to Sascha Corwin.
He wed art dealer Wallace in December 2008.