The 'X Factor' judge dated the late night talk show host before she married Ozzy Osbourne in July 1982 after meeting Jay in a nightclub when she first moved to Los Angeles aged 25.
Speaking on 'The Talk', Sharon confessed: ''I'm here, [and] I didn't have a boyfriend - I never did date a lot at that time anyway because I was not very dateable.''
The 60-year-old star - who has three children with Ozzy, Aimee, Kelly and Jack - admitted she prank called Jay until she finally plucked up the courage to meet him.
She said:''He liked my voice and I kept calling. I said I had the wrong number but I kept talking with my English accent, he actually came to my house and met me and we had a little fling.''
When pressed by her co-host Julie Chen if she slept with the 63-year-old talk show host, she remained tight-lipped as she joked: ''It was so long ago I can't remember! One cannot remember that long ago.''
Sharon claims her fling with Leno ended after he introduced her to ''real love of his life'' Mavis Nicholson, who he later married in 1980.
She explained: ''The fling was more of a fling for me and not fling enough for him because a couple of months later he brought around the real love of his life for me to meet, and she was lovely and they took me to Fatburger and showed me around town.''