Marquel Dawson, 19, said he was playing with his pit bull and German shepherd mix about 1:30 p.m. Wednesday in a nature area near their Fairfield home when they were attacked by the mountain lion, Sacramento's KCRA-TV reported Thursday.
"It was about the size of [a] German shepherd police dog -- like big -- about twice the size of my dog," Dawson said.
Dawson said he sprinted back to his house while his loyal canine held off the attacker and returned with the most useful item he could find in his garage: a ninja sword.
The teenager said the combination of the dog's tenacious defense and his own swordsmanship convinced the mountain lion to retreat from the battle.
Dawson said his dog was checked out by a veterinarian and suffered only minor injuries.
Animal control officials were investigating the incident.