Philipps, 33, is best known for her work on "Dawson's Creek," "Freaks and Geeks" and "Cougar Town." She is married to screenwriter Marc Silverstein, the father of her 4-year-old daughter Birdie Leigh.
Philipps announced her news by posting a photo of a positive pregnancy test on Twitter Monday.
"So this happened ...," she tweeted.
People.com confirmed the actress' pregnancy with her publicist.
The baby's gender and anticipated birth date were not reported.
Celebrity Families of 2014 [PHOTOS]