"After discussing my options with my wife, family and agent, I felt it was time to start a new chapter in my life," he said in a statement released Tuesday by his agent, Dan Lozano. "It has been an amazing journey ... So today, I walk away with no regrets.
"I knew this day was coming and over the last two years. I started to make my peace with it. I gave it my all and left everything on the field."
The 39-year-old Piazza batted .275 with eight homers and 44 RBIs as a designated hitter for Oakland last season, became a free agent and did not re-sign. He was not available to discuss his decision, according to Josh Goldberg, a spokesman for Lozano.
Taken by the Los Angeles Dodgers on the 62nd round of the 1988 amateur draft, Piazza became a 12-time All-Star, making the NL team 10 consecutive times starting in 1993.
He finished with a .308 career average, 427 home runs and 1,335 RBIs for the Dodgers (1992-98), Florida (1998), New York Mets (1998-05), San Diego (2006) and Oakland (2007).
His 396 homers are easily the most as a catcher, according to the Elias Sports Bureau. Carlton Fisk is second with 351, followed by Johnny Bench (327) and Yogi Berra (306).
Piazza thanked his family, teams and managers, some of his teammates -- and even owners, general managers, minor league staffs and reporters.
"Within the eight years I spent in New York, I was able to take a different look at the game of baseball," Piazza said. "I wasn't just a young kid that was wet behind the ears anymore -- I was learning from other veteran guys like Johnny Franco, who taught me how to deal with the pressures of playing in New York, and Al Leiter, who knew what it took to win a world championship."
He did not bring up two of the more memorable moments in his career: When the Yankees' Roger Clemens beaned him on July 8, 2000, and when Clemens threw the broken barrel of Piazza's bat in his direction in Game 2 of the World Series that October. Clemens denied intent both times.
"Last but certainly not least, I can't say goodbye without thanking the fans," Piazza said. "I can't recall a time in my career where I didn't feel embraced by all of you. Los Angeles, San Diego, Oakland and Miami -- whether it was at home or on the road, you were all so supportive over the years.
"But I have to say that my time with the Mets wouldn't have been the same without the greatest fans in the world. One of the hardest moments of my career, was walking off the field at Shea Stadium and saying goodbye. My relationship with you made my time in New York the happiest of my career and for that, I will always be grateful."