The 25-year-old has signed a provisional three-year contract with the Scottish outfit, where he spent four years before moving to Sale in 2011.
"I am very excited about rejoining Glasgow Warriors and working with Gregor Townsend and the coaching team at Scotstoun," he told the club's official website.
"I have learnt a lot from my time at Sale over the last couple of seasons but this is an excellent opportunity for me to return home and play my rugby in Scotland.
"Of course it helps that I know a lot of the guys in the squad already, but I've been watching their progress this season and it's a very exciting time to be getting involved with the club."
Vernon has won 20 international caps for Scotland.