Tavares, 29, has signed a short-term deal with the London side to reunite with manager Martin Jol, who previously coached him at Hamburg
He departed the German club in the summer, meaning he was available to sign outside of the transfer window.
Jol told the club's official website: “Mickael is a typical holding midfielder and I’m delighted that we’ve been able to strengthen this area.
"He played for me when I was at Hamburg so I’m familiar with his qualities and he will prove to be a very good addition.”
Tavares was born in Paris and started his career in the French lower leagues before representing Nantes and Tours.
He spent two seasons in the Czech Republic with Slavia Prague before signing for Jol's Hamburg in 2009, later spending loan spells with Nurnberg and Middlesbrough.
Tavares said: “I’m happy that I’m now officially a Fulham player and I’m looking forward to playing under Martin Jol once more.
"The players and staff have made me feel welcome and I can’t wait to get started with my new team-mates.”