The 31-year-old star showed off her new sleek figure this week at the Kardashian Holiday Party, posing for pictures alongside her younger sisters, Kim, 30, and curvy Khloe, 26.
Little sister: Kourtney kardashian, who has revealed she has lost 45lbs following the birth of her son, attended a party with her sisters Kim and Khloe over the holidays
She recently talked openly about how she shed the pounds in a new interview with America's OK Magazine.
Wearing a short bronze coloured cocktail dress with animal print high heels the reality star looked radiant and svelte.
'I love my new body': The star worked out with a trainer and ate small meals often to shed the weight
'I love my new body,' she told the magazine.
'They say it takes a full year to really get your body back and I believe that. I was 140lb when I gave birth and I'm 95 now. But for me it is about being a healthy mom and not being a certain weight.'
She also worked out as often as she could by running and doing strength training in the gym.
Sometimes she works out just by doing day to day things with her one-year-old son.
'I'd take him on walks when he was a baby and do squats while holding him,' she claims.
Like everybody, Kourtney admitted she does have some weaknesses when it comes to her diet.
'I'll eat Oreo Double Stufs, but I will have two instead of a whole box. And I love chips!'
Her sister Kim, who fluctuates between 8st 8lb and 7st 7lb (124lb and 109lb), has also been showing of a slimmer figure in recent weeks after getting back in the gym following a short break.
And baby makes three: Kourtney was joined by her boyfriend Scott Disick and their son Mason
The star revealed that she fell off the workout wagon at the end of the summer and only worked out once while filming her new reality show for eight weeks in New York with Kourtney.
But since the end of November, when she jump started her fitness regimen, Kim has been working out up to four times a week.