At one stage, 14 units of Dublin Fire Brigade fought the blaze, which started yesterday afternoon, as nearby businesses were evacuated.
Wong's Chinese restaurant in Ranelagh was gutted in the blaze.
Owner Alan Mann said staff will relocate to his other restaurants in Clontarf and Castleknock while the Ranelagh branch is closed.
One restaurant worker said the building became engulfed in smoke as they were preparing to open for the night
"There was a huge amount of smoke that came in and we ran out," he said.
Gardai say the blaze is not being treated as suspicious. It is thought it may have started in an office above the restaurant.
There were no reports of injuries. At one stage there were fears the roof would collapse, leading to the evacuation of the surrounding buildings, including McSorley's pub and the Wild Goose Grill.