Although circumstances surrounding Haile Selassie's death remain unresolved, his followers believe he was murdered.
A state burial will be held in the OrthodoxTrinity cathedral on Sunday - nearly 30 years after his death.
Haile Selassie died in mysterious circumstances after he was overthrown by Marxist military officers led by Mengistu Haile Mariam in 1974.
His remains were discovered after eight years but were never buried.
The Ethiopian Government gave the go ahead for the official funeral but accused the late emperor of oppression and brutality during his reign.
Unresolved mystery
The late emperor's coffin rested on a podium in the church, next to an underground chamber housing marble tombs of four other members of Ethiopia's imperial family.
Although circumstances surrounding Haile Selassie's death remain unresolved, his followers believe he was murdered.
"He was killed brutally because he was a good man, as all good men are killed," said the head priest celebrating the mass.
The service was attended by the emperor's daughter, Princess Tenangne Work, scores of his granchildren and hundreds of royal supporters.
There was also a Rastafarian delegation from Trinidad and Tobago. Rastafarians believe the emperor to be a god.
"We do not believe that he is dead. We communicate with him in spirit daily," said Bernard David Rooks, leader of the Rastafarian delegation.
"Haile Selassie is very much alive."
Brutality
Haile Selassie was crowned emperor of Ethiopia on 2 November 1930 and ruled with almost absolute power for 44 years.
His death was officially announced on 27 August 1975 and his remains reported to have been stuffed into a makeshift grave built under a lavatory, before being exhumed in 1992.
The government which toppled the Marxist rulers in 1991 reviled the emperor's reign describing him as a tyrant who enslaved the peasants by imposing a feudal system.
"Selassie's reign was marked by its brutality and extreme oppression of the Ethiopian peasants," the government said.
The government said it will continue with its efforts to recover money the emperor allegedly deposited in foreign bank accounts.