The 41-year-old made his Sao Paulo debut in 1993 and has remained loyal to the club throughout his 21-year career, scoring a goalkeeping record of 114 goals for them in more than 1,000 first-team appearances.
Ceni had originally planned to retire at the end of last season but signed a new one-year extension in December.
However, at a press conference on Friday, the Brazil international announced this would be his last season as a player.
"At the end of the year, I'm going to really stop," he said. "I'm not going to play again. This is my last year - not only for Sao Paulo, but as a professional footballer.
"I am feeling better now than at the same time last year. I feel good. There are a few aches but they are part of the game.
"I hope we have a different destiny in 2014."
Ceni was part of the Brazil squad that lifted the 2002 FIFA World Cup, and has won three league titles and two Copa Libertadores crowns.
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