The ex-Chelsea defender has been given time to recover from summer internationals and won't meet up with his team-mates until they return.
Geremi: "I am delighted to join Newcastle and I am very, very pleased with this move.
"This, like Chelsea, is a big club and a great football club. They have passionate fans and I look forward to playing for them.
"I was impressed with Sam Allardyce too. I was impressed with what he has done in football and his knowledge of other teams and players.
"It's a great move for me."