Fire crews from Preston, Fulwood and Penwortham were dispatched to the chip shop in Watery Lane shortly after 10am.
No one has been injured, but staff say the chip shop will stay closed through lunchtime after the incident.
Four fire engines attended and crews used a dry powder extinguisher to put out the fire.
A spokesper for Lancashire Fire and Rescue Service said: "Four fire engines from Preston, Fulwood and Penwortham were called to a fire in a commercial building on Watery Lane, Preston.
"Firefighters used one dry powder extinguisher to put out the fire. No injuries were reported."
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