The defensive midfielder has already passed a medical and will join his new team mates in training from Tuesday.
"I am looking forward to having Franca here and I am sure that he will be motivated and have a great deal of ambition to seek his chance with us," said Hannover coach Mirko Slomka.
"I have had exceptional experience with South Americans and treasured their determination and enthusiasm.
"I expect nothing less than the same from Franca."
Franca, whose full name is Welington Wildy Muniz dos Santos, will wear the number 16 shirt for the Reds and, according to their director of sport Jorg Schmadtke, he will bring more resolve to the midfield.
"With his six foot four inch, 88kg build, which he throws around vehemently during games, he has a strong physical presence," he said.
"He is a robust player who, in my opinion, will go a long way with us."
Hannover have already signed Johan Djourou and Andre Hoffmann this month.