Fire crews were called to the Hootananny venue in Church Street at about 17:20 on Monday following reports of an explosion.
The Scottish Fire and Rescue Service (SFRS) said firefighters quickly established that it was not a gas explosion.
SFRS said the incident was linked to a fireplace in the pub and a flammable liquid.
Miles Stubbs, SFRS Inverness watch manager, said a member of Hootananny's staff was taken to hospital.
He told BBC Radio Scotland that no-one else was hurt and fire crews dealt with the incident quickly.
Mr Stubbs said: "We turned out to Hootananny to reports of a possible explosion.
"On attendance we committed crews very quickly and offensively and ruled out quite quickly that it wasn't a gas explosion.
"There had been a small fire involved in a fireplace with some form of bioethanol fuel."
Following the fire, the owners of the city centre venue said on Twitter: "We are closed for the rest of today due to an incident this evening."
One person has been taken to hospital after a fire at a bar in Inverness.