Dan Donavan (81) bashed the home invaders with the traditional fighting stick after they broke into his home in Niles, Indiana.
He reached for the century-old shillelagh when he and his wife Barbara discovered their home had been broken into by local thugs.
The men had tricked the couple into letting them into their home by claiming to be from the phone company. They had asked to check their electrical box for an emergency.
But as the three men gathered in the basement, Dan said he became alarmed when he realised that two other men were lurking upstairs.
“I hear the floor in the bedroom squeaking and I yelled Dan! Dan! Somebody’s in our bedroom,” Barbara told Fox News.
Dan ran upstairs and found two men with a flannel pillowcase ransacking the house.
“Well, I couldn’t get to a phone, anything else. I had to go on offence to get them out of the house,” Dan said.
Dan said that, at that point, his grandfather’s shillelagh caught his eye and he decided to take action.
“It’s 100 years old. So if I hit him with this, it’ll make a point,” Dan said.
“Yeah, I hit the guy in the head. I’m certain I got him in the head good because he wouldn’t let go of the pillowcase,” he said.
“It was the only place I could get a clear swing was in the driveway.
"But I’m chasing them barefoot and swinging the stick like a madman,” Dan said.
News reports say Niles Police are still looking for the men and say there have been a large number of so-called ruse entry robberies recently in the area.