The appointment represents a first move into coaching for the 38-year-old defender, who will also continue playing.
Dunlop and Gormley were team-mates at Alloa Athletic and the new recruit says he is delighted at being given the chance to work at Vale
Dunlop tweeted: “Looking forward to my first venture in coaching and a combination of playing also.
"I have known David Gormley from our playing days at Alloa and when I received the call from him to become his assistant it was an easy decision to make.
"I hope my experience of playing at senior level for many years helps the squad this coming season. I’m looking forward to a successful season at Rossvale.”
Dunlop takes over from Sean Higgins who resigned from his role as Gormley’s assistant last month due to family and work commitments.