Flanker Tu'ifua has started training with the Falcons, and Tait is enthused by his arrival at Kingston Park.
"We haven't had a player of his stature for quite a while," Tait told the club's official website.
"I am absolutely ecstatic that he decided to sign for us, as we had been holding out for this sort of player and we have finally got our man.
"He's a big man, a good ball-carrier and will give us so many dimensions to our set-up."
Tu'ifua, 27, played in every game of Samoa's World Cup campaign, while he also starred during their victory over Australia earlier this year.
"I had offers from around Europe, including clubs in France, but I heard a lot about Newcastle and its ambition," he said.
"I've chosen Newcastle, and I am looking forward to bringing my family across here."
Newcastle, currently bottom of the Premiership, recently added South African lock Adriaan Fondse to their squad, while Tongan World Cup wing Suka Hufanga will link up with them shortly.
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