"I am delighted that Jimmy has agreed to come and help me as my new assistant manager," manager Barry Fry told the clubs official website.
"Jim did a fantastic job here as a player and he only left to become manager of Swindon Town. He had the heartache of missing out at Wembley in a play-off final with Reading.
"He is one of the few coaches in the country to have a professional diploma, which is the highest coaching award anyone can be given. I am sure he will have a big impact both on and off the field at London Road."