The Expendables 2 star was at Heming's side when she gave birth to daughter Mabel Ray Willis on Sunday in Los Angeles.
Willis's spokesperson told People: "[The couple] are overjoyed about the newest member of their family. Both mother and baby are healthy and doing beautifully."
Heming and Willis first announced that they would be having a child together in October 2011.
The pair recently celebrated the third anniversary of their March 2009 wedding in the Turks and Caicos Islands.
Willis also has three daughters from his 13-year marriage to actress Demi Moore.
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