The 27-year-old brings experience from spells in Belgium and Switzerland and is expected to add depth and creativity to Bremen's midfield.
Peter Niemeyer, Werder's head of professional football, said: "The opportunity came up for us to sign Cameron and we're delighted that we were able to get this season-long loan deal agreed.
"He has shown his quality during his spells in Belgium and Switzerland and can definitely help us this season."
Head coach Horst Steffen added: "Cameron can play across the midfield. At his last club, he showed that he is a goal threat as well as someone who can create for others. He has both quality with the ball at his feet and a good tactical understanding.
"He is also very quick and doesn't shy away from a tackle. We're very happy that he's joined us."
Puertas becomes Bremen's final addition of the summer and is expected to compete for a starting spot in the Bundesliga and DFB-Pokal campaigns. The club have emphasised his versatility, noting he can slot in both central and attacking midfield roles, giving Steffen more tactical options as the season begins.
With training underway, Puertas has joined a squad keen to build on last season's strong performances. Bremen supporters will hope his creativity and energy can help lift the team in the opening months, as the club aims to push for European qualification.
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