Leah announced the happy news on Instagram debuting a photo of her baby bump, reported Ace Showbiz.
In the photo, Leah could be seen caressing her baby bump while being kissed by Brandon on the cheek.
The 32-year-old TV personality wore a green cleavage-baring, flower print dress and her hair was styled in loose waves.
She captioned it, "Well, it's time we share the good news. We're having a baby."
Brandon tied the knot with Leah on May 31, 2012 in Hawaii outside the St Regis Princeville Resort.
The couple, who performs in the indie pop group Brandon & Leah, has appeared numerous times on "Keeping Up with the Kardashians". Their single "Showstopper" was used as the theme song for the third season of "Kourtney and Kim Take Miami".