Nottinghamshire Police have said the blaze is in a derelict building.
A statement said: “Emergency services are currently dealing with a fire in a derelict building on Curzon Street in Nottingham city centre.
“The incident happened at around 11.28am today (Sunday 31 May). Police and fire crews are currently at the scene, and a number of cordons will be place around Huntingdon Street and Curzon Street.
“The cause of the fire is not yet known. There are no reports of any injuries. As a precaution, we are looking at evacuating a number of properties on the street.
“We are sorry for any inconvenience this may cause. We are asking people to avoid the area while the incident is being dealt with.”