In an interview with the American Association of Retired Persons, Ronstadt, 67, said she experienced symptoms for years before she got a diagnosis.
"I couldn't sing, and I couldn't figure out why. I knew it was mechanical," said the singer known for songs such as "I Can't Help It (If I'm Still In Love With You)," "Hasten Down the Wind" and "Blue Bayou."
"I knew it had to do with the muscles, but I thought it might have also had something to do with the tick disease that I had. And it didn't occur to me to go to a neurologist. I think I've had it for seven or eight years already, because of the symptoms that I've had. Then I had a shoulder operation, so I thought that's why my hands were trembling."
She said she was "completely shocked" when she finally got the diagnosis. She said she now uses poles for support when she is walking on rough surfaces and a wheelchair when she is traveling.
Ronstadt has won 11 Grammys with many more nominations, two Academy of Country Music awards and an Emmy. She was nominated for a Tony and a Golden Globe award for her performance as Mabel in the Gilbert and Sullivan operetta "Pirates of Penzance."
Her book, "Simple Dreams: A Musical Memoir," is to be published in September. She told AARP the book does not discuss her battle with Parkinson's.
While she had high-profile relationships with California Gov. Jerry Brown -- the first time he was governor -- and with "Star Wars" director George Lucas, Ronstadt has never married. She has two adopted children.
AARP plans to publish the full interview next week.