An unidentified woman broke into Simon Cowell's west London home and rifled through his belongings in his bedroom and bathroom while he was downstairs watching TV.
'It was an absolutely terrifying experience. Seeing this woman standing there in my house was like something out of a horror movie," said Cowell.
"It was frightening but I'm going to take it as a warning. In some ways I've been lucky. You have to look on the positive side because it could have been a whole lot worse.
"I now know that I need to improve my security. She could have had a gun," Cowell told the Daily Mail.
The Sun reported that Cowell was "pretty shaken up" after the woman smashed his window and entered the house armed with a brick.
According to the Mail, the woman went from room to room inside his £9m property and entered his bathroom.
A woman named as Leanne Zaloumis, 29, has been arrested.