The music mogul, who famously axed Cheryl from the US version of the show in 2011, is said to have wooed her back with a butler service dinner over the weekend.
"It was just him and Cheryl," an insider told The Sun. "Simon was offering an olive branch. It was a very civil evening.
"She was happy and loved talking about the show. It's pretty much nailed on that she'll be back."
Simon Cowell and Cheryl Cole
Simon, 54, confirmed his own return for the eleventh series of the UK talent show just last week, but has yet to announce his fellow judges.
The insider added that Cheryl could be revealed as a returning judge "within weeks."
Simon, who reportedly fired Cheryl because viewers stateside couldn't understand her thick Geordie accent, is said to have offered the Newcastle-born star a £2million pay packet as well as free reign to verbally abuse him.
"Simon is ready for the fury of Cheryl onscreen," another source told the Daily Star. "He has made it clear she can say what she wants to him, and get the fans booing and hissing him at any stage.
"Obviously fireworks on-screen between the pair could make for astonishing viewing and Simon knows that."
Simon and his pregnant girlfriend Lauren Silverman
Father-to-be Simon, who is expecting his first child with socialite girlfriend Lauren Silverman, said that he was "thrilled" to be making his return.
"It's been three years since I last judged the competition and I'm excited to find a global superstar again," said Simon.
"Despite all the rumours, ITV and the producers have not decided on the rest of the judging panel quite yet," he added. "You'll just have to wait and see."