The 37-year-old actress, whose younger sister is New Girl star Zoey Deschanel, confirmed the news to US Weekly after Emily was spotted with the beginnings of a baby bump.
Emily and her husband David Hornsby are parents to son Henry
All eyes were on LA-born Emily, who is also famed for promoting veganism and advocating animal rights, when she stepped out at The Conscientious Table event at Crossroads Kitchen in September displaying a noticeable bump and again in November when the navy shirt she wore to the P.S. Arts Express Yourself event appeared to be straining over her tummy.
Emily tied the knot with It's Always Sunny in Philadelphia actor David in LA on 25 September 2010.
Emily appeared to have a baby bump at recent events
"I have a great nanny who is there with me all day, every day," Emily previously revealed when asked about how she juggles working and being a mother by Mom.Me. "[Henry] will come to set and hang out just off camera.
"I can't say he's been silent the whole time," she added. "But I have a wonderful situation where I get to see my baby throughout the day, and I can't imagine leaving him home at this point. But I know so many friends who have regular jobs and can't take their baby to work, so I feel incredibly, incredibly lucky."