The 30-year-old joins Csaba Laszlo’s side until the end of the season after a successful trail period.
The Tunisian returns to Scottish football almost three years after leaving Rangers.
His final match saw him hit the headlines for all the wrong reasons as he kicked and punched Motherwell striker Lee Erwin immediately after Rangers were defeated at Fir Park in the play-off final.
He was given a seven-match ban by the SFA, though this was served after he joined French club Angers.
Dundee United sit in third place in the Scottish Championship and have won just one of their last five league fixtures.