The Grey's Anatomy lead revealed on social media last night that her daughter Sienna May Ivery had been born in August by surrogate, and thanked her co-stars for helping her to keep the new arrival under wraps.
"I would like to thank my @ShondalandTV family for helping us enjoy these first few weeks privately," she wrote.
Ellen already has one child with husband Chris Ivery, five-year-old Stella Luna.
The star shared a beautiful picture of Chris kissing their new arrival, captioned, "We love you more than words can say."
Architectural Digest magazine also published a gorgeous picture of Sienna's nursery, with its bright and inviting colour palette:
Ellen says she is smitten with her growing family. "I try my absolute hardest every minute of the day to be the best mother I can to those children," she said in an interview.
"Not having a mother growing up, being a mother is more significant than I can put into words," she added.