Two fire crews from Birley Moor and Aston Park fire stations were called to a disused garage fire on Rectory Road at Killamarsh.
As crews arrived at the scene at 10pm on Wednesday night the garage had already spread to a second garage.
Firefighters used a hose reels to put the fire out.
The fire is believed to have been started deliberately.
Fire crews left the scene at 11pm.