The return of the three-time most valuable player, who last season had the Vikings one win from an appearance in the Super Bowl, will mark his 20th season and ends months of speculation about whether or not he would retire.
"I was so close to getting these guys to the Super Bowl," the 40-year-old told a news conference at the Vikings' training camp in Minnesota. "I felt I owed it to this organization to give it one more try."
Favre said he hopes to play on Sunday when the Vikings face the San Francisco 49ers in an exhibition game.
The NFL's all-time leading passer, who worked out with the team on Wednesday, said he has nothing to prove and that his decision to play another season was all about his team.
Favre said he has been thinking: "You are so close ... let's do it together ... let's finish this together."
Three of Favre's team mates flew this week to his hometown in Mississippi to bring him back for one more season and on Tuesday they all boarded a private plane for Minnesota.
In one of the best seasons of his long career, Favre led the Vikings to a 12-4 regular-season record last year before losing in the NFC championship game after a Favre interception halted a Vikings drive late in regulation.
An ankle injury suffered in that game required surgery in May and held up a decision on his return.
The surgery has made the left ankle a little better, but the gray-haired Favre admitted there was no part of him that was 100 percent any more.
"I can't promise I can make it through the season," said Favre. "But if I am going to play, I am going to play at a high level."
(Writing by Gene Cherry in Raleigh, North Carolina; Editing by Frank Pingue)