The Black Sabbath frontman, 65, has a lot of respect for the talent show creator and tried the wrinkle-erasing procedure after learning Cowell used the injections to preserve his looks.
However, the tattoo-loving rock icon was put off by the pain of being prodded with a needle and he never returned for a second session.
He tells Britain's Event magazine, "(I) like him (Cowell). (He) says what he thinks. I had Botox because he's a big fan of it. But they stick a needle in you and it b**ody hurts, so I didn't do it again."