The police said the person was around 1.7 m tall and unusually white-skinned, had black hair with a crew cut, and was wearing a gray short-sleeved T-shirt at the time of death.
Based on preliminary examination, the police determined that the victim's carotid artery had been cut with a sharp object more than 10 cm long causing him to bleed to death.
The victim was not a resident of Phu Quy Island and is thought to be a tourist from the mainland.
Authorities have yet to determine if it was a case of suicide or murder.
Officers from the mainland will arrive in Phu Quy on Tuesday for a forensic examination and work together with the local police on the investigation.
Located on the north of Phu Quy Island, Cao Cat Mountain is one of the tallest mountains on the island, about 106m above sea level with dangerous cliffs and rocks of unique shapes.
Due to low profile, the mountain area is always deserted.
Phu Quy Island, 120 km southeast of Phan Thiet in the south central coast, was pristine until at least five years ago, when its natural beauty started to draw crowds.