Clark County spokesman Erik Pappa says about 30 of them were hospitalized for heat-related injuries Friday afternoon at Van Warped Tour at Silverton Casino.
He says most of the others "were essentially provided shade and water and a place to sit down."
There were no reports of any life-threatening injuries.
As the numbers of people with problems grew, medical workers at the scene called for help from surrounding agencies.
The National Weather Service reported temps of 115 Friday, part of a heat wave affecting several Western states.
The Las Vegas Sun reports that responders aided an additional 35 people with heat problems around the city, including seven taken to hospitals.