No one was in the restaurant during the blaze, and there were no injuries.
Crews responded to the scene, Cave Man Kitchen at 807 W. Valley Highway, at about 4:30 a.m. Tuesday after receiving a report of a fire at a business.
Within an hour the blaze was brought under control.
The extent of damage and the cause of the fire remain under investigation.
The restaurant owner, Roseann Donley, told KOMO Newsradio she's thankful the fire wasn't worse and that no one was hurt. She says the restaurant has about 20 employees and she hopes to reopen soon.