Officials said that all of the occupants made it out of the large house at 3380 Willamette St., which had been divided into three separate occupancies.
One person had to be helped out of the house by a firefighter.
The fire caused significant damage to one of the units. Eugene/Springfield fire said that a quick and aggressive attack allowed crews to stop the flames from burning the other two units in the tri-plex.
Officials at the scene said they believe a fire in a fireplace spread through a crack in the brick and mortar.
The whole house suffered significant smoke damage, and everyone living at the residence was displaced. Officials said the Red Cross and EWEB stepped in to help those living at the house.
Four fire engines, a truck company and a medic responded to the scene. The state fire marshal is now heading up the fire investigation.