The wreckage of the Marines UH-1Y Huey helicopter, which had gone missing on May 12, was found three days later on a steep slope near dense forest high in the mountains.
Six US Marines, two Nepalese soldiers and five civilians were killed in the crash, Reuters reported.
"Because of the terrain and bad weather the helicopter ... collided with hard rock and crashed about 11,200 feet (3,413 meters) above the sea level in Kalinchok," Nepal's army said in a statement late on Friday, following a joint investigation with the US military into the accident.
The helicopter was part of a huge international relief and rescue operation for the victims of the earthquake that struck Nepal on April 25.
The quake and a second tremor on May 12 killed at least 8,832 people and injured more than 22,000.