The deal has been in the pipeline for some time, with boss Martin O'Neill alluding to it at his news conference on Monday and the club later confirming the 29-year-old had signed until the end of the season from Saudi Arabian club Al-Hilal.
Mangane joined Alfred N`Diaye in moving to Wearside during the transfer window, with O'Neill saying: "Kader is player who will add to the overall strength of our squad and give us options. He will improve competition for places and we are delighted to welcome him to the club."
He added: "We're short of players at the moment and what I'm hoping he will bring is competition for places, which is pretty important at any football club.
"But we have had a few injuries at this time of year and you don't want to leave yourself short.
"He is prepared to come and battle for a place in the team so that's encouraging. We're just adding competition for places and that will make us a bit more healthy."
However, O'Neill played down talk of a move for Toulouse midfielder Moussa Sissoko, who has been linked to both the Black Cats and Newcastle during this transfer window.
O'Neill said: "I can talk about players who have come to the football club, like Alfred, or who are nearly there but I can't talk about some player who might be a million miles away."
Mangane spent five seasons in France with Lens and Rennes before moving to Al-Hilal in 2012.
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