The man and a companion were stuck in their car on a remote road within the national park, rangers said. They then set off on foot across salt flats to reach a busier road.
The 68-year-old stopped after 2km while his companion reached the road and was helped by a motorist.
Park rangers launched a search, but came too late to save the man's life.
"This is a heartbreaking reminder of how quickly conditions here can turn dangerous," Death Valley National Park Superintendent Mike Reynolds said as he expressed his condolences.
"Death Valley is an extraordinary place, but its heat, distances and remoteness can be dangerous, regardless of experience. We're grateful to everyone who took part in the search, and our thoughts are with his loved ones."
The park service warns visitors of extreme summer heat in Death Valley and urges visitors to exercise caution, noting mobile phones do not work in many parts of the park.
Some roads are only suitable for off-road vehicles.
Travellers are advised to carry sufficient water and if their cars break down, it is generally safer to seek shelter in the vehicle search teams can spot more easily than a pedestrian in open terrain.
Death Valley is one of the hottest places on Earth and forecasters say temperatures in the region could rise to over 47C over the weekend.
