Marquel Dawson, 19, said he used the sword to fight off a mountain lion who was attacking his dog Stunna.
This happened in a field behind Dawson's house in Fairfield.
The afternoon started out with a simple game of fetch. The dog, a pit bull German Shepherd mix, went into a bush area and it was there he found the mountain lion.
"It was about the size of German shepherd police dog -- like big -- about twice the size of my dog," Dawson told KCRA television.
Dawson ran home and grabbed the sword out of his garage.
Although Stunna had the upper hand at first, Dawson said the mountain lion was winning by the time he got back.
He whacked the cat with his sword and finally got him to release.
The veterinarian taking care of the dog kept him overnight, but he's expected to make a full recovery. His biggest injury is a cut to his mouth and a gash to his head.
The vet said the dog suffered minor injuries considering the circumstances.
Investigators with the Department of Fish and Game said they aren’t positive the attack was a mountain lion. It may have been a bobcat. They said they will return Thursday to continue the investigation.