The 31-year-old has signed a two-year deal for an undisclosed fee.
"It's official. Steed Malbranque is a St Etienne player. The midfielder is committed to ASSE for two seasons," read a statement on the Ligue 1 club's official website.
The Frenchman signed for Fulham from Lyon in 2001 before spells with Tottenham Hotspur and the Black Cats.