The 32-year-old reality star - who already has a two-year-old son Mason - says she and boyfriend Scott Disick, 28, feel blessed.
Kourtney told E! News: 'We feel so blessed to be having a little girl and to be able to share this new experience with Mason.'
Maternal: Pregnant Kourtney Kardashian, pictured out in Calabasa last week, has revealed her unborn child is a girl
Earlier this month it was rumoured Kourtney's unborn child was a girl.
'Kourtney was hoping for a girl,' an insider told America's Life & Style at the time.
'She loves having a boy but thinks having a girl would be perfect so she can dress her up and show her the ropes in life.'
Disick previously told the magazine: 'A girl would be a fantastic addition to our family.'
The couple are also the parents of two-year-old son Mason Dash, who was born in December 2009.
Growing brood: Kourtney with Scott and their son Mason in New York back in September
Meanwhile, Kourtney's happy news has been slightly dampened by a cold which has infected the entire Kardashian clan.
Kourtney has blamed Scott for 'passing around' the illness, with few members of the close-knit unit managing to avoid it.
She wrote on twitter page: 'Who is passing around sick germs in the fam like it ain't no thang? @KhloeKardashian & I are sick & now @KylieJenner. @ScottDisick is the ONE!(sic)'
She added she was glad to have a film to watch while she rested and battled the symptoms.
She tweeted: 'OMG I'm on day 3. It's horrible. At least Boogie Nights is on. (sic)'
Half-sister Kylie Jenner also tweeted: 'Don't feel good. One gets sick. We all get sick (sic)'