There was no evidence of intent by the boy who accidentally ignited brush outside his home by playing with matches, the Los Angeles County District Attorney's Office said in a statement.
Authorities are referring the case to the Department of Children and Family Services to determine if further steps are necessary. No other information about the investigation was released because the case involves a minor.
The blaze was among more than a dozen major wildfires that blackened over 800 square miles from Los Angeles to the Mexican border. In all, 10 people were killed directly by the wildfires.
About a week after the fires were ignited, sheriff's department officials announced that they had interviewed the boy, who lived with his family in a trailer home on a ranch in Santa Clarita, and that he acknowledged starting the blaze.
Officials presented the case to the district attorney's office, but law experts had said prosecutors would have trouble getting a conviction against the boy because it would be difficult to prove intent to cause harm.