Sean Penn and Jewel "fell in love" while he was on a break from now ex-wife Robin Wright.
The 41-year-old singer claims she and the Oscar winner, who had an on-again, off-again relationship with the 'House of Cards' actress from 1989 until their divorce in 2010, had a passionate romance in 1995.
Recalling their first encounter in her new memoir 'Jewel - Never Broken: Songs Are Only Half the Story,' the blonde beauty revealed: "He had seen me on 'Conan' and was working on a movie he'd written called 'The Crossing Guard'. He wanted me to compose a song for it. I told him I would and he said he would meet me anywhere to screen the movie, I could name the day. I gave him my cell number and figured I would never hear from him again."
But their friendship blossomed into something more after Jewel wrote the track 'Emily' for the movie.
She added: "We spoke on the phone a lot and he was a fantastic flirt and I did not mind one bit. But I was no fool and knew I was most likely a trifle to him. I intended to give him no such conquest. I put that man through his paces and he took it in stride. He began to court me in earnest, following me around on tour, acting as my de facto roadie."
The duo secretly attended the Venice Film Festival together at the time and Jewel said: "Sean took me to see the sights in Montartre and wrote me in notes that he hid in my pockets...I enjoyed Sean and would eventually fall in love."
The 'Mystic River' actor, 55, ultimately decided to reunite with Robin and married her in 1996 before they split for good five years ago.
Jewel was married to Ty Murray, with whom she has four-year-old son Kase, for six years before they split last year.