The 29-year-old has spent his entire career in France, but has admitted that former France international Johan Micoud convinced him to make the move.
"Johan is an icon in Bremen. He is an important contact for me and advised me to make a switch to Werder," Obraniak told the club's official website.
"We know each other well, we both live in Bordeaux. He said that my style of play would fit in superbly in the Bundesliga.
"We spoke about life in Bremen too. He only said positive things about the people, the city and the club."
Obraniak has signed a two-and-a-half-year contract.