The pair both wore thigh-split dresses for the bash, as they took along partners Scott Disick and Kanye West.
Clearly all that boob flashing wasn't enough for one weekend for Kim.
The 34-year-old - who just got back from her Las Vegas birthday bash - stunned in a light pink shimmery gown, showing off her toned leg and a whole lot of cleavage.
Meanwhile pregnant Kourtney proved she's possibly the most glamorous expectant mum ever in a long thigh-split black number, and appeared happy as she posed with her sibling and partner.Scott and Kanye looked suitably moody but suave nonetheless as they kept a protective arm around their stunning ladies.
Reality star Kim posted a snap with her sister and Scott, writing: "Date night #SartianoWedding #Scott&Allie."
Meanwhile Kourtney added her own of the foursome, and wrote: "Adjusting the slit. #sartianowedding."It comes after Kim spent the night in her favourite Vegas hotspot TAO with her hubby and sister Khloe, in possibly the most revealing dress we've ever seen.
We know we say that a lot, but who can argue this time?
She posed in the risky number before heading inside with a VERY happy Kanye and partying all night with some of her nearest and dearest.
While it was all a bit too old for baby north, Kim made sure he was close to her heart throughout, and wore an adorable 'Nori' necklace for the event.
