He fell severely on his back and was taken to hospital where they identified several breaks and rushed him into surgery.
A spokesperson for Cowell said: “Simon broke his back in several places when his bike fell while testing a new electric bike in the yard of his home in Malibu with his family.
“He was taken to hospital where they operated overnight, is under observation and is doing well. “
It is understood that the surgery began on Saturday evening Los Angeles time.
A source said: “The operation was successful, but Simon will be in the hospital for a while to recover. ”
Entertainment mogul Cowell lives with his six-year-old son Eric, along with his partner Lauren Silverman.
Last month, it emerged that Cowell had bought out Sony Music Entertainment’s stake in television shows, including Britain’s Got Talent and The X Factor.
This decision allows the music mogul to acquire ownership of all international versions of The X Factor and Got Talent programs.
The Got Talent format airs in 76 markets, while The X Factor airs in over 130 territories.
Sony Music’s stake in the business was transferred to Syco Entertainment, a company wholly owned by Cowell.
Filming for this year’s Britain’s Got Talent next stop has been postponed due to the coronavirus crisis, but ITV has said it hopes to continue the series later this year.
Simon had started cycling with the aim of improving his fitness after a previous fall at his home three years ago.
The star has vowed to exercise and adopt a healthier lifestyle after suffering a frightening fall in 2017.
He had to be kicked out of his London mansion by paramedics who came to his aid when he fell down the stairs on his way to the kitchen in the wee hours of the morning.
Simon said the terrifying incident was a “wake-up call” that caused him to change his ways.