De Laurentiis was slicing a turkey roll Saturday during the episode, which also featured Alton Brown, Bobby Flay and Ina Garten, when the knife slipped and she cut her finger, Radar Online reported.
"She seemed to go pale and got very quiet putting pressure on it and whispering to Ina that it was bad," an eyewitness told the website. "She looked like she was about to faint."
The show broke for a commercial shortly after and when the show returned, Brown said De Laurentiis had left the set to receive medical attention. She later returned with a bandaged finger.