A crew from Aston, assisted by Rotherham and Maltby attended the blaze at 8.20pm last night in Lindleys Croft.
The man was working on the classic car when it is thought that a piece of material accidentally caught on fire.
A South Yorkshire Fire & Rescue spokesman said the man tried to put out the blaze with an extinguisher in its early stages but called for assistance when it started to spread quickly.
The fire caused significant damage to the garage contents.
A South Yorkshire Fire & Rescue spokesman said: “Crews from Aston, who arrived first on the scene, followed in support by Rotherham and Maltby attended the incident on Lindleys Croft in Todwick about 8.20pm last night.
“Firefighters with breathing apparatus dealt with the blaze and went into the adjoining property to check for further fire.
“Crews left the scene around 10.10pm after we secured the garage and the surrounding dwellings at risk.
A spokesman added that the fire was accidental but a formal investigation is set to be carried out.