The crew member was a male diver working in a water tank on the movie's Los Angeles set when he drowned, reports TMZ.
He was pulled out of the water after someone discovered him in the tank not breathing. After 911 was called, emergency responders found the man in full cardiac arrest when they arrived at the scene.
He was flown to a nearby hospital and pronounced dead upon arrival.
A spokesperson for the film's studio, Disney, said: "We regretfully confirm that a Lone Ranger crew member has passed away after being taken to a local hospital.
"Our full support is behind the investigation into the circumstances of this terrible event."
The Lone Ranger, starring Johnny Depp and Armie Hammer, is a remake of the 1950s television series.