Cox said Friday he began talking with general manager Frank Wren about the extension after last season.
"Recently [Wren] said let's get a deal done, and we got a deal done very quickly and simply and I'm thrilled to be back," Cox said.
Cox, 67, is the winningest manager in franchise history. He is in his 27th season as a manager, including 23 years with the Braves, and has said in recent years he has started to think about retirement.
But he said Friday he's not ready to leave the game.
"I'm certainly going to end my career here," Cox said. "There's no doubt about that now. I'm happy. We've got great ballplayers. They're fun to be around and it's a fun team to be a part of. If it wasn't fun, you should get out of the game, but I'm still having fun."
Cox led the Braves to 14 straight division championships from 1991-2005, including the 1995 World Series championship.
"It's just year to year and we'll see," Cox said of possibly managing after 2009. "I still have a great passion for the contest of baseball and it's still a lot of fun."
Cox said there was no discussion of extending the contract more than one year.
"Year to year is perfect," he said. "[Wren] did say I want you here while I'm here."
Wren said he's excited that "one of the most respected managers in all of baseball will again be managing our club in 2009."
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