The former Bolton Wanderers, Charlton Athletic and Blackburn Rovers player, 34, has failed to feature in Paul Jewell's first-team plans at Pride Park so far this season.
Cobblers boss Stuart Gray told the club's official website: "Andy has a fantastic pedigree and a lot of experience.
"I've been looking to add a player with experience to help us defensively and Andy brings a lot of knowledge, organisation and leadership with him.
"He will strengthen us for what is a very busy month ahead and I am sure he will prove an asset to us."
Striker Scott McGleish, 34, has extended his loan stay at the club until the beginning of January.
McGleish who ended his first stay at the Sixfields Stadium when he moved to Wycombe in January 2007, will remain with the Cobblers until January 3.
During his first spell with Town, McGleish scored 54 times in 126 starts for the club, but has found the net only once in five appearances for Stuart Gray's side in the last month.