The happy couple - who already have two-year-old daughter Hazel - waited until America's Fourth of July (04.07.16) to confirm the arrival of their daughter, who they've named Violet and was born just two weeks ago.
The 36-year-old actor announced the exciting news on Twitter.
He wrote: "What a better way to celebrate 4th... than to announce our 4th family member!!! 2 weeks ago we met our beautiful daughter Violet #Happy4th (sic)"
The 'Into The Woods' star and her hunky husband - who she married in 2010, and lives with in their family home in Los Angeles - first announced they were expecting a second child in January.
The brunette beauty previously admitted that she had forgotten she was pregnant because she was too busy looking after Hazel.
She said: "The first pregnancy is the most self-indulgent thing in the world because you get massages and prenatal yoga and hypnotherapy CDs. During this one I forget that I'm even pregnant. I'm hoisting a two-year-old around!"
Meanwhile, Emily previously revealed motherhood has caused her to rethink about what acting roles she will choose in the future.
She said: "Too racy would be one thing I wouldn't go for now. I'm not so keen on doing nudity, because I'm not 22 any more. And actually it's not so much a moral thing as 'I've done it before and do I really want to do it again?'
"Does it serve the film or is it gratuitous and seeing someone's t**s for the sake of it? Because I don't think it's necessary most of the time. Also playing violent or racist characters would be hard for me now.'"
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