The blaze broke out at about 3pm on the first floor of Sunkiss Beauty & Tanning at the top of Chapel Walk, which faces onto Fargate. Heat from the flames caused windows to shatter and sent black smoke pouring onto the street, forcing several businesses to close due to the smell and smog.
Fargate was also partly taped off and bus and tram routes were blocked by six fire engines which flooded High Street and Church Street.
At one point no fewer than 30 firefighters were at the scene helping to tackle the fire in sweltering heat.
A turntable ladder was also used to dampen down the inside of the building after the flames were extinguished.
Brave firefighters wearing breathing apparatus searched for casualties inside but no one was hurt in the incident.
It is not yet known how the fire started. Scroll down to view photos from the scene.
Sunkiss Beauty & Tanning said the store was “badly damaged” and will be closed “for the time being while we work on it”.
A South Yorkshire Fire & Rescue spokesperson added: “The fire involved a beautiful Victorian building on Chapel Walk, which was very badly damaged inside.”