Police confirmed they had received a call around 12.50pm to a kitchen fire in the TGI Friday’s restaurant on the corner of Castle Street and Rose Street, in the capital’s west end.
Staff and residents of surrounding flats were evacuated, with some sections of Castle Street and Rose Street cordoned off while firefighters tackled the blaze.
Crews carried out a detailed search of the building while others tackled the fire from above using turntable ladders.
Witnesses reported seeing plumes of smoke pouring out of the back of the restaurant on a lane off Rose Street, with others saying the smoke could be seen on Princes Street.
The restaurant kitchen is situated in the basement of an annexe attached to the back of a tenement block. Part of the roof of the annexe collapsed in the fire.
The fire service confirmed that there had been no casualties.
The extent of the damage is still unclear, but neighbouring properties have been affected by smoke and water.
Building control staff from the council were on site to check the safety of affected structures.
Darrell Wade, chief operating officer at TGI Friday’s, said: “We can confirm that a fire broke out within the property that we occupy on Castle Street in Edinburgh. We immediately evacuated our restaurant and all guests and team members safely left the building.
“We are now working closely with the Edinburgh fire service to help understand the cause of the fire. At this stage the exact cause and location of the breakout is inconclusive.”
A spokeswoman for the Scottish Fire and Rescue Service (SFRS) said: “Firefighters conducted a thorough search of the premises and confirmed no one remained inside the building.
“Crews are continuing work to extinguish the fire which caused extensive damage including the partial collapse of the building’s roof. An investigation into the circumstances surrounding the incident will be conducted by SFRS.”