Around 40 adults and 25 children were praying when the man, armed with a sawn- off shotgun, entered the Compassion Centre in Ballymun at around midday.
Worshippers at the Christian outreach centre were forced to lie on the ground after being threatened by the gunman.
The raider ordered them to empty their pockets and stole money and valuables before making his getaway in a blue Fiat Punto that he demanded from a member of the congregation.
He threatened to shoot any of the born-again Christians attending the event who refused to hand over their possessions.
Missionary Daniel Tabb, who works at the church that helps the homeless and those addicted to drugs, was addressing members when the man burst through the door.
Mr Tabb said the man put his gun to people’s necks, heads, and stomach and ordered them to give him their possessions.
“He was obviously a very desperate man to do something like that,” said Mr Tabb when recalling the event during an interview on RTÉ radio yesterday.
Mr Tabb sid he used his body to cover his wife and two young children when they were all lying on the ground.
Senior pastor John Eniola said the man put a gun to one of the member’s heads, gave him a bag, and told him to collect the money and phones before fleeing
Mr Eniola, who had been sitting at the front of the building, said the man — who was wearing a balaclava — came in through the back door.
“For a moment it was frightening because the man was carrying a gun,” he said. “We have never seen anything like that before but we pray for him, we forgive him and we would like to see him in church.
“We knew it was a robbery because he was threatening and just asking for wallets and money. If it had been a terror attack it would have been different. Thankfully nobody was hurt. ”
Gardaí have CCTV footage showing the man entering the building and have taken witness statements.
After abandoning the stolen car in nearby Poppintree, the raider removed his balaclava and gardaí are hoping people who saw him in the area will help gardaí to identify him.
Anyone with information can call Ballymun Garda Station at 01 6664400 or the Garda Confidential Line at 1800 666111.