The couple, who are already parents to son Mason, four, and daughter Penelope, 23 months, stepped out together at Party Under the Stars, an event host by Women's Health magazine.
Kourtney drew attention to her baby bump in an eye-catching white lace jumpstuit, while Scott kept his look casual in jeans and a checked shirt.
Kourtney and Scott are expecting their third child together
LA-born Kourtney, who is currently away from home filming Kourtney & Khloe Take The Hamptons, confirmed that she was expecting again in June, during an episode of Keeping Up With The Kardashians.
The 35-year-old was seen breaking the news to her long-term partner Scott at the end of the episode, in a montage of clips showing viewers what to expect during the forcoming new season. "I'm pregnant," she says. "It was not a plan."
Rumours were rife that Kourtney was planning to expand her family, with a source telling US Weekly that the brunette beauty claimed she "wants to have a handful of kids."
Kourtney and Scott's baby, whose gender is not yet known, is reportedly due in December.