, 24, has been on loan at Bremen for the past season, which saw him appear in all 35 of the club's competitive fixtures and finish as their joint top scorer in the league on eleven goals, alongside Aaron Hunt.
"Waiting a long time for this"
"We're delighted that Nils will be continuing to go for goal wearing the Werder crest over the coming years," sporting director Thomas Eichin said; "He's shown this season that he fits in perfectly here. We know he's got tremendous potential and now with this long-term arrangement, we're confident he can maintain his progress and become a cornerstone of the team in Bremen."
For his part Petersen, who was snapped up by FC Bayern after finishing as Bundesliga 2 top scorer (25 goals) for FC Energie Cottbus in 2010/11, commented, "I've been waiting a long time to get this news and I'm very happy it's worked out the way I'd hoped. I'll be going into the new season highly motivated and want to play my part in helping us take a major step forwards."