West Sussex Fire and Rescue Service said it was called to a fire between Railway Approach and Teville Place at around 7.20am.
A spokesman said: "We sent two fire engines from Worthing to a fire at a taxi office garage.
"It has been confirmed as a fire in the loft space and there has been ten per cent damage by the smoke.
"We used four breathing apparatus, two hose reels and a smoke curtain to prevent oxygen getting into the room when the door was opened."
The fire service confirmed the fire was started accidentally and crews left the scene at 8.05am.