It emerged on Monday afternoon that the 43-year-old was due to leave the Saddlers for another club, with Bristol Rovers and Northampton Town linked.
But instead Clarke has made a shock move to nearby rivals Vale who sit 18th in the division. It has been agreed mutually and Vale will pay Walsall for Clarke's services.
Clarke has spent nearly two years at Walsall after joining in May 2019. His assistant Brian Dutton has been promoted to head coach and will be assisted by Mat Sadler and Maik Taylor.
A Walsall statement read: "We wish Darrell all the best for the future. Chairman, Leigh Pomlett, will communicate with supporters by video message tomorrow ahead of our game with Cheltenham Town."