Athletic director Charlie Cobb announced Fox's hiring Tuesday.
Fox spent the past 13 years on Bob McKillop's staff at Davidson and was his associate head coach the past two seasons.
Before that, the 40-year-old Fox was a high-school coach in New York.
Cobb says Fox's ''winning pedigree speaks for itself.''
Fox replaces Jason Capel, who was fired last month following a 9-21 season. The Mountaineers are moving into the Sun Belt Conference next season.
• Appalachian State fires head coach Capel