He made 196 appearances for Chelsea and also counted Reading, Portsmouth and Exeter amongst his eight clubs.
"He started his coaching career at Swindon before I managed to get him to Bristol City as a development coach," said boss Gary Johnson.
"He is a good coach, he is ambitious and I enjoy his company as I am sure the players will."
Johnson added: "I had to bring someone in who would fit in well with the players and the club and I am pleased we have been able to get him to Northampton Town.
"I think he will be a big asset and I am delighted to be able to appoint him as my number two."
His appointment fills the gap left by Malcolm Crosby, who departed Sixfields along with a host of players in May.
Source: BBC Sport
Source: BBC Sport