Donna Iliffe-Pollard created a petition, which gained over 8,000 signatures, after she saw scenes of Mel B's boys category swimming with the animals and worried it would 'glorify captive dolphins'.
After Simon saw the petition, he tweeted to insist he had no idea that dauphins were being used of filming and said the footage would not be used.
He said: "Reading your tweets. I had no idea Xtra Factor producers filmed with dolphins. This will NOT be showed on Saturday [sic].
"I think you all know my view on cruelty to animals so thank you all for your concern.
"I want to send this out regarding the Xtra Factor team. They are a hard working bunch who weren't aware of the growing concerns regarding dolphins."
Animal rights group PETA thanked Simon for his cooperation. They told the Mirror: "Simon has always been a good friend to animals, so it's no surprise to PETA that he has intervened to prevent The X Factor from glamourising swimming with dolphins.
"Many of the highly intelligent and social animals incarcerated in these sad displays have endured the trauma of being caught and torn away from their families before they are sold into a life of captivity.
"In the wild, dolphins swim together in family pods for their entire lives. We're very grateful to Simon for taking a stand against these cruel marine displays and encourage everyone to visit SeaWorldOfHurt.com to learn more about why dolphins and other cetaceans don't belong in captivity."