Romano, 32, shared the good news on Facebook, posting that the couple have named their little one Isabella.
"Brendan and I are more than thrilled to announce the birth of our daughter, Isabella, on December 24 at approximately 4 pm Merry Christmas everyone," she wrote.
Romano and Rooney tied the knot in a winter ceremony in 2013.
The couple announced in June that they were expecting their first child, due on Christmas Day.
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