The 36-year-old singer and her husband David Foster have become proud parents to a "healthy baby boy", a representative for the couple has confirmed.
The spokesperson told People magazine: "Katharine McPhee and David Foster have welcomed a healthy baby boy. Mom, Dad and son are all doing wonderfully."
The news comes just days after Katharine let the news slip she would be welcoming a son into the world during a chat with Roxy Manning and Tammin Sursok on their Women on Top podcast, when she said there are "different issues" she needs to think about when raising a boy compared to a girl.
She said: "Now that I am having a boy, there are different things I need to worry about to teach him versus the things I would be thinking about with a girl. But it's kind of refreshing because I feel like I don't need to think about those societal 'this is the way you look.' I think men have different issues and different things to worry about."
Katharine had previously hinted she was expecting a boy back in December, when she posted a picture of herself showing off her baby bump whilst wearing a blue coat, and captioned the snap with two blue love hearts.
Back in October, sources confirmed Katharine was expecting but the couple hadn't announced the happy news until her post on Instagram.
Meanwhile, 71-year-old David - who already has five children, Allison, 50, Amy, 47, Sara, 40, Erin, 38, and Jordan, 34, from previous relationships - previously described his wife as the "whole package".
He said: "She's the whole package, you know? Singing, acting, beauty, she's got it all!"
Shortly after their wedding in June 2019, Katharine decided to take David's surname because she loves the "traditional" nature of taking a partner's last name.
She explained: "I'm a romantic. I've always liked the idea that it's still a traditional thing that exists in our society. I like the idea. I think it's romantic and it's a great last name ... We've been away since we've been married, so not [yet], but I love it. I just love the ring of it, so I'm enjoying it."