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.
'Obviously Messi is the best player in history and being compared to him means that you're doing things right, but I try to be myself': Barcelona star responds to comparisons with Argentine legend
'Darwin Nunez would be gold for Arsenal': Liverpool legend claims Gunners should have signed Uruguayan striker in January
