The 37-year-old "Perfect" hitmaker shared the news on Instagram by posting a picture of herself with a growing baby bump.
"Surprise," wrote Pink, who is already a mother to five-year-old Willow Sage Hart.
Earlier, the three-time Grammy-winner also revealed that she is planning to give her daughter, a sibling.
"My brother is everything to me. So I want her to have family beyond her papa and me. For that reason, I mostly want another one for her to have a lifelong friend."
The 37-year-old singer added that she loves the idea of having a big family.
"Family is the most important thing. And my best friend Grant has, like, four brothers and sisters. I love it- it's like holidays, the chaos, the fighting, the mom always having a kid around. For sure. I want to adopt, I want to have more - just, yes.