Chimbonda, who moved to White Hart Lane from Wigan for £4.5million in August 2006, is the second Spurs player to move to Wearside this summer following Teemu Tainio's switch.
And Keane believes Chimbonda, who was a non-playing member of France's 2006 World Cup squad, will be a useful addition to the squad.
"He'll give us more options at the back, creating more competition for places there, so all-in-all it is a fantastic signing for us." he told the club's official website.
"Pascal is one of those rare players who can play anywhere across the back line and that will be invaluable to us, so naturally we are very pleased to secure his services.
"He has a lot of Premier League experience which can only be a plus for us."