Steve Davis will be number two to manager Gudjon Thordarson at Gresty Road.
Davis succeeds Neil Baker, who is set to take up a new position at the club.
A one-time Stoke City trainee, Davis was one of Dario Gradi's first signings at Crewe in 1983.
He told BBC Radio Stoke: "I'm very modest about what I do, but I've worked very hard in my time at Nantwich.
"They're in great shape to continue their success."
Crewe chairman John Bowler said, "I'm delighted to welcome Steve back to the club and I'm sure he will make a major contribution to the future success of Crewe Alexandra."
Manager Thordarson was delighted with his new number two, as he told BBC Radio Stoke, "He's a simple, straightforward, hard-working man and he's worked hard to gain success in the lower leagues. I'm pleased to get him and I look forward to working with him."