The blaze was sparked around 1 p.m., and firefighters said the restaurant, located in the 1600-block of East 11th Street, was open and full of customers at the time.
About 25 to 30 people were reported to be inside.
Employees tried to fight the fire until officials arrived. The cause of the fire is unknown.
The damage was so extensive that the restaurant won't be able to reopen until the entire structure has been rebuilt.
"Fifty percent of the structure is gone," said Siler City Fire Chief Scott Murphy. "The kitchen area mainly, the truss, roof is gone. We've got some air conditioners tilting in. So, we're trying to keep firemen out from in there, so it doesn't fall on them."
No one was reported to be injured.