The 'Titanic' star was one of the 20 guests staying at the Great House on Necker Island, along with her boyfriend Louis Dowler and her two children, when the fire broke out.
Branson, his wife and son Sam, 25, were sleeping in a nearby building when the timber Great House burst into flames at 4am on August 22 after being struck by lightning during a hurricane.
Despite dense smoke, Winslet, 35, joined in the rescue operation picking up the elderly woman in her arms and leading her away from the blaze, reported Mirror online.
"Many thanks to Kate Winslet. It was she who carried my mother out of the house. She swept her up into her arms and got them out of the house as fast as possible.
"My mum is 90 and can walk but it was more to speed the process up than anything else. But Kate was great. She said it was like being in a film set where you're waiting for the words 'cut' but they just don't come. It was quite surreal for her to be in a real-life situation like that," Branson said.
The 61-year-old businessman, who bought the Great House for 180,000 pounds when he was just 28, said he wants to rebuild it as soon as possible.
