The 36-year-old reality star confirmed the news Thursday in a teaser for Keeping Up with the Kardashians Season 14 following months of surrogacy rumors.
"What happens every time I say, 'Guess what?'" she asks sister Khloe Kardashian on the phone.
"The person's pregnant?" Khloe responds before Kim announces, "We're having a baby!"
People reported this month that the woman Kim and Kanye hired to carry their child is pregnant. The surrogate is due in January, according to TMZ.
"The entire family is over the moon. Kim had been looking for a surrogate for months until recently when she found the perfect candidate," a source told People.
"They want everything to be perfect and for the baby to be healthy," the insider added. "They don't want any complications."
Kim and Kanye already share 4-year-old daughter North West and 21-month-old son Saint West. The couple explored surrogacy after doctors told the reality star it would be unsafe for her to carry another child.
"After talking to Kanye, I think I always knew that surrogacy was an option, but I didn't think it was that realistic of an option, and now I feel like that's my reality," she said on an April episode of Keeping Up with the Kardashians. "I feel like surrogacy really is the only other option for me."
Khloe herself is reportedly expecting her first child with boyfriend Tristan Thompson. In addition, news broke last week that Kim and Khloe's sister Kylie Jenner is pregnant and expecting a baby with boyfriend Travis Scott.