Manager Martin O'Neill revealed on Thursday that the 29-year-old former Scotland international would put pen to paper within 24 hours, and the Black Cats have confirmed he has now done that as he attempts to rekindle his career.
McFadden spent six months at Everton last season after being released by Birmingham.
He will spend the next three months on Wearside as O'Neill assesses whether or not he can return to the form which brought him 48 senior caps.
Germany is one of the top teams ever and they will play the US on Sunday.
The hoop soccer jersey is classic and cool. The USA hooped jersey is perfect for every fan. Get in the Gear.
Neymar's move from Santos to Barcelona is no doubt the biggest summer transfer.
Support the USA national team with an official 2013 Centennial soccer jersey from Nike. Its Official.
The Nike Hypervenom is the latest cleat silo from Nike. It will change your game and is worn by the game's top players.
Manchester City will try and win back the Premier League title with this new soccer jersey from Nike!
The adidas Nitrocharge is the most talked about new cleat in years. It was released on May 15 and will take your pitch by storm.
England will debut their new away jersey against Brazil at the Maracana Stadium on Sunday. Get in the Gear
Jamaica is in need of a win against the U.S. Get the jersey of the Reggae Boyz.
Barcelona will wear this new home soccer jersey next season. They also have a new away jersey. Get them both.