Borowski, who won 33 international caps and scored twice for his country, has been suffering with a recurring problem in his right ankle and felt unable to continue his professional career.
The midfielder sustained the injury in October 2010 but failed to recover from surgery on the injury.
He made a final appearance for the club on the last game of last season - his first in the Bundesliga in 2011-12 - and his contract was not renewed this summer.
"I had a wonderful time as a footballer with many great, emotional moments," he said. "I'll always keep that with me."
Borowski graduated from the Bremen academy and but for a single season at Bayern Munich in 2008-09 spent his entire career at the club.
He won the German double in 2004 and also represented Germany at the 2006 World Cup and Euro 2008.
Borowski says he hopes to stay at Bremen in a non-playing capacity, adding: "Werder is my club. I am in discussions with the leaders and I will probably know more about the future in a month."