The 29-year-old completed his expected move to the North East club on a free transfer following weeks of training with the Premier League outfit.
"I'm delighted," McFadden told the club's official website. "This is a good chance to get back playing football and hopefully earn a longer-term contract.
"I've enjoyed my short time here so far and hopefully I can get the chance to play games and do well. I already knew some of the lads but the dressing room has been very welcoming. I felt settled from my first day so it's been good."
McFadden was released by Everton at the end of the season.