The midfielder, whose contract was set to expire next year, joined Nuremberg from Saarbrucken in 2008 and helped the club into the Bundesliga in his first season.
Frantz made 109 top-flight appearances for the now relegated Nuremberg, scoring eight goals, and Freiburg sporting director Jochen Saier believes the player will be a perfect fit at the club.
"We had very good discussions with Mike Frantz, where it quickly became clear that he fits very well the type and the attitude that suits us," he said. "We believe that he will help our team with his quality, experience and versatility."
Frantz himself added: "SC Freiburg is a club that has established itself in recent years in the Bundesliga," he said. "I hope that I can help the club and the team with my experience.
"I've always been impressed by the way Freiburg play their football.
"It was always uncomfortable to play against Freiburg, so it's all the more enjoyable that I can now play for the club."
