The X Factor judge opened up to Susanna Reid on Good Morning Britain about life since becoming a father in 2014, when his partner Lauren Silverman gave birth to their son, Eric.
The 56 year old said: 'I'm great with puppies, I'm not great with babies, because like a puppy will respond, babies at a certain age don't do anything so when he was about five or six [months old] I was like... I just don't know what to do!'
Like many new parents, Simon spoke about his initial fears when Eric was born and said of his mini-me, 'He wasn't reacting to me and I thought maybe he hates me.' However, those initial worries faded as he went on to explain, 'They said, "No, take your time." And then one day they are talking, listening, responding and also they sort of become a bit like you. Which I don't know is a good thing or a bad thing! He's a funny little thing.'
While Simon is normally used to sharing his expertise on music, he told Susanna he's also been passing on his words of wisdom on fatherhood to One Direction's Louis Tomlinson, 23, who is expecting his first child in 2016.
Louis Tomlinson is expecting his first child with Briana Jungwirth in early 2016
'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 and it will change your life for the better." And that's it.'
Aww, it seems TV's 'Mr Nasty' is actually a bit of a softie at heart!