She detailed how the two first met, when her career was just starting out and he was on a break from his now-ex-wife Robin Wright.
According to the excerpt obtained by E! News, Jewel recounts how Penn reached out to her after her first TV appearance on Conan O’Brien’s show in 1995. He wanted her to compose a song for his film "The Crossing Guard."
Jewel ended up writing a song called "Emily" for the flick, and their romance began soon after. She called him a “fantastic flirt” but she added she intentionally moved slowly at first.
She also says she preferred him when he was sober.
"I liked his mind sober, and had fun playing this way,” she wrote. “When I told him this in all seriousness, in a dive bar after a sound check, he responded with a melancholy stare and then canary-eating grin and said it would be impossible not to fall in love with me. I looked at him to see if he was serious. It seemed he was."
Jewel recalled a trip to the Venice Film Festival together, writing that he "took me to see the sights in Montmartre and wrote me sweet notes that he hid in my pockets."
"I enjoyed Sean and would eventually fall in love," she added.
But the romance was short-lived. Penn eventually got back together with Robin Wright, whom he married in 1996. They had two children together before they split in 2010.
Jewel married Ty Murray in 2008, but filed for divorce last year. They have one son together.