Video posted on Vogue.com shows three people tying her into the garment that gave her the hourglass shape.
It was so tight, Kardashian said she had to stay standing for part of the night.
“Okay so Anna, if I don’t sit down for dinner, now you know why,” Kardashian says in the video. “I’ll be walking around mingling, talking, but I cannot hardly sit. I can only half-sit.”
Some had postulated online that Kardashian had ribs removed to achieve the look, but her trainer shot back at the rumors, defending her client.
"To make things clear," Melissa Alcantara said on her Instagram Story. "1. This dress is corseted BUT 2. Kim trains her ass off 6 days a f***ing week, she wakes up early AF and is dedicated."
Corsets are having a resurgence in recent years.
Inside Edition visited Orchard Corset in New York to test one out.
Watch the video above to see the results!