The 32-year-old star – who already has 23-month-old son Mason with her boyfriend Scott Disick – is "thrilled" to be expanding her family and providing a sibling to her first child.
She said in a statement to E! Online: "Scott and I are so excited to announce that we are expecting our second child and are thrilled to be expanding the love in our family."
Kourtney recently began a new web series entitled 'Kourtney's Mommy Blog' where she unveils what she has learned as a mother.
She has previously claimed she is never happier than when she is spending time with her son, and struggles to do things without him.
She said: "Unless I'm working, I can't be away from him without feeling guilty. It doesn't feel good or natural to be, so it's a struggle.
"I don't want to judge, but I've also met women who think it's cool to be out or away from their baby, and I don't get that. Every time I'm not working, he's with me. Even on an airplane, he is with me even if the nanny is also on the plane. Any time I can have with him, I am lucky to have."