Lebanese officials said on Friday the helicopter crashed into a mountain near the village of Niha in eastern Lebanon's Bekaa Valley.
The Lebanon army command said that a military committee has begun an investigation into the incident.
The official National News Agency said the helicopter might have experienced a technical fault that caused the crash on Friday.
The helicopter was an American-made Bell 205 - one of 16 Bell helicopters belonging to Lebanon's air force.
The victims were identified as air lieutenants Hadi Sadaka and Albert Moussalam, air warrant officer Raymond Aziz and private Nizar Obeid. All four belonged to the air force.
"Contact with the military helicopter was lost at 1025 local time while it was on a training mission," the military said in a statement.
"It appeared that the helicopter was subjected to an air accident that caused it to crash over the Niha-Bekaa hills which resulted in the death of the plane's crew."
The father of one of the victims was killed in a similar crash. Lieutenant-Colonel George Sadaka, father of Hadi Sadaka, died when his helicopter crashed into the Mediterranean in 1988, the military official said.
President Emile Lahoud spoke by telephone with Army Commander General Michel Suleiman to offer condolences over the death of the four soldiers.