The 5ft brunette, who gave birth to daughter Penelope in July, has lost 44lbs and is now a slim size 8, weighing around 106lbs (7 1/2 stone).
But the mum-of-two said she had to work hard to get her body back in shape.
"It was harder to lose weight the second time around," she said. "I gained 44 pounds with Penelope."
Already a mum to three year-old son Mason, Kourtney says she stuck to celebrity trainer Tracy Anderson's 90 minute dance workouts to lose the weight.
Kourtney will no doubt be sharing her pregnancy and parenting tips with younger sister Kim (32), who last week confirmed she is expecting a child with boyfriend Kanye West.