The 1988 National League MVP revealed the news Tuesday in a statement released by Fox Sports Detroit.
"I have faced many different obstacles in my life, and have always maintained a strong belief that no matter the circumstances, I could overcome those obstacles," Gibson said. "While this diagnosis poses a new kind of challenge for me, I intend to stay true to my beliefs. With the support of my family and friends, I will meet this challenge with the same determination and unwavering intensity that I have displayed in all of my endeavors in life. I look forward to being back at the ballpark as soon as possible."
The 57-year-old Gibson was fired in September as manager of the Arizona Diamondbacks after four-plus seasons. He now calls Detroit Tigers games for Fox Sports Detroit, but Gibson hasn't been in the broadcast booth since Opening Day on April 6 while undergoing tests.
Gibson had one of the most memorable moments in baseball history with his limping, pinch-hit home run in the ninth inning of Game 1 of the 1988 World Series for the Dodgers. He also won a championship in 1984 with the Tigers, where he played 12 of his 17 major league seasons.
"It was a shock to all of us," Diamondbacks president and CEO Derrick Hall said before Arizona's home game against Colorado. "Gibby means a lot to this organization. He had a couple of wonderful years here as manager and is always going to be a part of this family.
Hall promoted Gibson from bench coach to manager during the 2010 season.
"It's got to be devastating news for him as it was for us," Hall said. "But he's got plenty of family and friends to support him and especially right here with the D-backs."
Former Dodgers teammate Mike Scioscia, the Angels' manager, called it "a sad day."
"He's always been a competitor and I know he'll never give in," Scioscia said. "To hear what his battle is now with Parkinson's, it's really sad. I know he's going to give everything he has and he'll keep going and get back on the baseball field. That's what he loves. He loves being on the field."
The Tigers released a statement wishing Gibson the best and saying they are hopeful he'll be back at the ballpark soon.
"Tremendous person, he's always been great to me. One of the fiercest competitors I've ever watched. Just feel awful for him and his family," Detroit manager Brad Ausmus said. "I can't see Kirk Gibson folding up shop and crawling into a corner. I don't think that's in his DNA."
Parkinson's is a progressive disorder that gradually takes a toll on the nervous system. Notable figures with the disease include Muhammad Ali and actor Michael J. Fox. Former major league All-Star Dave Parker revealed in 2013 that he was dealing with Parkinson's as well.
"That's hard. I know Kirk," Pittsburgh manager Clint Hurdle before the Pirates' game in Chicago. "I know Kirk from back playing minor-league ball together. He's always been up for a challenge. You never want to see anybody have to meet this challenge. ... What a competitor. What a good man. Good man to have in the game. Good man to know. ... I will reach out to him."
Diamondbacks manager Chip Hale was the third base coach in Arizona when Gibson was bench coach. Hale said he learned a lot from Gibson and shared good times and conversations with his friend.
"He's going to just attack this thing with the same fervor that he's had," Hale said. "We're all pulling for him to be OK ... It's just hard when you hear about that. "
Diamondbacks players expressed their sympathies via Twitter.
Michigan football coach Jim Harbaugh also tweeted about Gibson, referencing a football game Gibson played for Michigan State at Michigan.
Gibson receives Parkinson's diagnosis
Jayson Stark discusses the outpouring of support from the baseball world for former player and manager Kirk Gibson, who has Parkinson's disease.