The 56-year-old "X Factor" judge asked Tomilson to enjoy the fatherhood, reported People magazine.
"I just said, 'Enjoy it'. If I had been his age and someone had said, 'You're going to have a baby,' I'm not sure how I would have coped with it. But he did call me and I said, 'When you've embraced it, you'll be amazed how much you are going to love it. It will change your life for the better'," Cowell said.
Tomlinson, 23, is expecting his first child with stylist Briana Jungwirth early next year.