Flames were shooting out of the windows of a vacant home on Sunday evening before 7 p.m.
Santa Barbara Fire sent several engines, including a ladder truck, to the scene.
They had the fire controlled in about 15 minutes, even as the flames were visible throughout the downtown area.
No one was hurt and it's unknown how the fire began.
Investigators reviewed video from the Smart and Final grocery store across the street to determine who had been around.
The street was closed off for a block as the fire crews battled the flames and mopped up.