The model and her musician husband John Legend are already parents to two-year-old Luna, who now has a little brother to contend with.
Teigen took to social media on Thursday to make the announcement.
Teigen, 32, and Legend, 39, who are also parents to two-year-old daughter Luna, revealed they were expecting a second child in November previous year - a boy.
The couple announced the birth on Twitter this morning, with Chrissy posting "Somebody's herrrrrrre!" with happy face and baby bottle emojis.
Explaining why she had reached her final tether, Chrissy said that things were more frustrating because she had known about her pregnancy for so long.
Before adding: "Wanna hold my boy let's do thisssssss'".
"Luna, what's in here", Teigen asked her daughter.
She captioned the sweet photo of them together: "A splash with toons".
Venting her frustration on Twitter, she wrote: 'Happy pregnant Chrissy is gone. meet OVER IT Chrissy. A boy. So. Yeah'.
They explained: 'Luna's gonna be an issue.
"She's used to being the centre of everything right now so we'll see how she adjusts to sharing the spotlight".