Speaking on a panel promoting Roman Polanski's new drama at the Venice Film Festival, the actress recalled shooting the scene, which sees her throwing up during an argument about her son.
"I had to contain a lot of vomit in my mouth, which is not possible for a person to do. So without going into too much detail, it was a fairly complex rig and there was some extremely clever CGI involved," Winslet explained.
"It was hysterical… We were all completely beside ourselves with laughter."
Winslet added that she brought her real-life children to the set to witness the scene, saying that they "literally have not stopped talking about it since".
Carnage, which will make its US premiere at the New York Film Festival later this month, also stars John C Reilly, Jodie Foster and Christoph Waltz.
Winslet recently escaped a major fire at Sir Richard Branson's holiday home on Necker Island and has been credited with helping his 90-year-old mother reach safety from the blaze.
Watch the trailer for Carnage below: