The 32-year-old becomes Les Verts' fourth signing of the summer, following the arrivals of Renaud Cohade, Francois Clerc and Romain Hamouma.
ASSE have been linked with a handful of strikers this summer as they searched for partner for star forward Pierre-Emerick Aubameyang. Bolton's David N’Gog had been linked with the club, as had Guillaume Hoarau of PSG.
Brandao has had successful spells with Shakhtar Donetsk and Marseille, and has the kind of experience the Ligue 1 club were looking for.
"Everyone knows Brandao's qualities. He is a player who works hard, [he's] a warrior," said Saint-Etienne CEO Roland Romeyer.
“Throughout his career he has scored important goals," Romeyer continued. "I remember his goal against Lyon last season in the final of the League Cup and one against Inter Milan which helped OM reach the quarter-finals of the Champions League. His record speaks for itself."
After helping Marseille to the Ligue 1 title in his first season, Brandao was twice sent out on loan to Brazil last year. He returned to Marseille in January but was released at the end of the season in a cost-saving move by the club, who have experienced financial difficulties of late.