Hinkel has been without a club since the expiration of his contract with Celtic at the end of last season.
The German international is thought to have signed a deal until the end of the season with the option of a further 12 months.
The 29-year-old was happy to make the move to Freiburg as he bids to get his career back on track.
"I am very happy that I have signed for Freiburg and the waiting is over," Hinkel told the club's official website.
"I want to give my best and do all I can to ensure Freiburg stay in the top-flight."
"I am very pleased to return to Bundesliga action and it is great that I have joined such a well-run club."