The bodies were found Monday night near Goleta, police said. All had been stabbed repeatedly.
Police released few details about the killings. A news conference Tuesday morning was postponed because officials said they were trying to reach the victims' families.
The suspect was identified only as a 46-year-old man.
The house is on a dead-end street in a residential neighborhood near Foothill Elementary School.
The bodies were found around 11 p.m. Monday by Santa Barbara County sheriff's deputies responding to a call to the house. Police have said they are not looking for other suspects.