The 27-year-old Frenchman has been linked with a move to the Cottagers all summer and joins after Boro signed Julio Arca from neighbours Sunderland this week.
Queudrue, who has joined his new colleagues in Austria, told Fulham's website: "I really enjoyed my time at Boro, but decided that it was time for a new challenge. I met with Chris Coleman and was impressed with his ambition for the future at the club."
Queudrue has signed a contract to keep him at Craven Cottage until 2010 and manager Coleman said: "Franck is a quality defender and one that I have admired for some time.
"He is a gifted player with great skill, and I know that he will make a difference to our back line.
"I am planning for the future here at Fulham and I know that the additions we have made this summer and back in January have increased our chances of long term success and I am very excited about the future."
very good signing for fulham..they need help in the defence and by signing queudrue is even better..4 year deal and a good pick up for fulham..