The music mogul has seen his worth swell to £300 million to put him in eighth place in a league of music millionaires compiled for the new Sunday Times Rich List, which will be published at the weekend.
Topping the music list - as he did last year - is London-based Ukrainian businessman Len Blavatnik, whose empire includes the Warner Music Group which was acquired in 2011. He is estimated to be worth £10 billion.
Simon's value will have been boosted by a new deal with ITV for further series of The X Factor and Britain's Got Talent, and appears not to have been seriously dented by the stage flop of spoof musical I Can't Sing! - for which he was one of the backers - which closed after a matter of weeks.
Tomorrow night Britain's Got Talent is back for its eighth series featuring acts from across the south. David, Alesha, Simon and Amanda Holden are all back for the talent show. Our reporter Divya Kohli was invited to take a sneak peek at the first episode - and to talk babies with Simon!
The music mogul from Sussex, aged 54, had jetted over to New York and was by his partner's side as she gave birth shortly before 11pm.
A spokesman for the X Factor judge said: "They are all OK. Simon was there for the birth. He landed at 6.15pm, British time, and he was at the hospital by about 7.15pm.
"He was there for the birth."
He said details about the baby, including how much he weighed, were not available yet.
Simon Cowell is returning as a judge to ITV's X Factor it's been confirmed.
More to follow.
Simon Cowell is to return to the X Factor as a judge for the show's 11th series.Read the full story ›
Simon Cowell gets a soaking from fellow Britain's Got Talent judge Amanda Holden after the pair disagree about a pair of contestants.
She holds a glass of water above his head in the ITV show, threatening to pour when the show boss refuses to put a singing duo through.
And when he digs in his heels and fails to change his mind, she tips the glass over him as the panel splits along gender lines - leading to Amanda and Alesha Dixon later storming off during the auditions.
Divya Kohli has been waiting in the wings to bring you all the latest behind the scenes gossip. She's been talking to Amanda Holden, Alesha Dixon and, of course, Simon Cowell. And she reveals an interesting fact about him.
Yes, Britain's Got Talent is back on our screens tonight. The judges - including Amanda Holden - who's from Chipping Norton, in Oxfordshire, and Simon Cowell, who's originally from Sussex, are back and ready for action.
Divya Kohli went along to the star studded launch. Here's her extended interviews with Amanda Holden, Alesha Dixon and Simon Cowell.
Divya Kohli interviews Amanda Holden, Alesha Dixon and Simon Cowell.
The star quit the panel to work on his US version of the show and has not been a judge for the past two years but in an interview with Hello! magazine he promised he would be coming back.
Cowell, who will be back on screens next month with the return of Britain's Got Talent, said: "I'm definitely getting more involved and will have a role in the next series.
"I'm not going to lie - I do miss doing it, because it's like my baby.
"It's been difficult the last two years not being on the show as I always had a great time and the last time that I did do it, it was such a brilliant year. So at some point of course I'm going to come back and do the show."