Crews from St Mary's, Redbridge and Hightown fire stations were called to the Grade II listed South Western House, which is now occupied by a restaurant, club and the city's most expensive apartments, at 11pm last night.
Staff who work at the Grand Cafe- a restaurant and bar, were in the basement at about 11pm when they spotted a blazing fire coming from the laundry room.
They kicked the door down and threw water on the blaze, firefighters said.
Although they managed to put out the fire, the basement was filled with thick black smoke and firefighters have today spoken out to highlight the safety message “get out and stay out.”
Crews were on the scene in Canute Road for more than an hour last night to clear the dangerous smoke logging, which filled the lower floor of the building.
Firefighters said they did not have to evacuate residents or diners- and no apartments were affected. The blaze caused damage to the laundry area of the basement.
It is not thought to be suspicious.
Crew manager of St Mary's fire station Peter Clarke, said: “The actions of the staff prevented a potentially awful situation and they acted bravely and it is commendable however we must stress if you see a fire don't tackle it.
" Call us up, close the doors if you can and get out and stay out.”
Once Southampton's grandest hotel, the South Western House was used by first class passengers of the Titanic and its history dates back to 1865.
Among the Titanic passengers who stayed here was J Bruce Ismay- the controversial head of the White Star Line.
The building looks directly out over the docks.