The 32-year-old reality star was also accompanied by her sister Kim as they mingled with a host of celebs at the viewing event held at West Hollywood Park tonight.
Kourtney and 30-year-old Victoria's Secret model Alessandra looked incredible in their respective white and beige gowns.
Sisters together: Kim Kardashian slipped into a form-fitting black gown with cut out triangles as she posed next to her pregnant sister Kourtney at Elton John's Oscars viewing party held in West Hollywood Park tonight
Bumps on display: Kourtney and Victoria's Secret model Alessandra Ambrosio both posed with together as they cradled their burgeoning bumps
They both posed together inside for the cameras, cradling their bumps having announced their pregnancy just a month apart late last year.
Kourtney already has a two-year-old son, Mason, with boyfriend Scott Disick and they will add to their brood with a baby girl.
She revealed earlier this week they were delighted after discovering that a sister was on the way for Mason after finding out the sex of their unborn child at a recent scan.
Getting in on the action: The pair accessorised their looks with lots of jewellery. While Kim wore her hair loose, Kourtney's was held up in a bun
Mingling: Kim and Khloe joined I Want To Have Your Babies singer Natasha Bedingfield, who looked lovely in a black lace dress
Wining and dining: Kim joins a host of stars at the dinner table, including Heidi Klum, seen in yellow
She and her Californian businessman fiance Jamie Mazur already have a 14-month daughter Anja.
Tonight's event, held in association with AIDS Foundation, also saw the likes of Katy Perry, Miley Cyrus, Heidi Klum and Natasha Bedingfield attend.
Perry and Miley both played it demure in a departure from their more usual revealing attire.
Reality star pal: Kim was also accompanied by her friend Jonathan Cheban of The Spin Crowd
Smouldering: Kim owned the room as she sauntered around in her eye-catching ensemble
Happy family: Elton posed with husband David Furnish, son Zachary and business magnate Robert Kraft (R)