Brian Straw, 57, was threatened by a knife-wielding man who lunged across the counter of his shop in Pall Mall, Chorley.
But instead of handing over the money, father-of-three Mr Straw fended him off with the truncheon that he keeps under the counter.
“Whether what I did is madness or bravery, there’s a fine line sometimes,” he said.
Police are now appealing for information about the incident, which they believe is linked to another robbery in Chorley.
Mr Straw, who has owned Premier News for the last 18 years, said: “I’d been here since 4am.
“This guy came in and I realised he wasn’t a customer because he had his face covered. He just came out with ‘Give us your money, open the till’. There’s nothing in the till anytime, it’s kept low for on purpose. He was in my face with a knife. He was saying ‘I’ll use it on you’.
Mr Straw, who keeps the truncheon for protection, continued: “My first thought was, it’s not a case of him not having the money, it’s a case of him coming in disrespecting my honour really and I was going to fight for that.
“I just challenged him with an old police truncheon I have.
“I just kept fending him off, trying to get the knife off him.
“He was very challenging. But eventually he realised he wasn’t going to get anywhere. He ran out.”
The terrifying incident was captured on the shop’s CCTV.
“Whether what I did is madness or bravery, there’s a fine line sometimes,” added Mr Straw.
The incident happened on Good Friday. Around 11.20am the same day, police said a man entered Collingwood Convenience Store, Collingwood Road, carrying a knife.
He threatened a staff member, a 50-year-old woman from Chorley, before removing cash and coins from the till and making off.
The offender in both incidents is described as male, wearing a black jacket over a grey hooded top with a snood covering his face. He also had black trousers, black footwear and black gloves.
Det Con Phil Hampson, of Skelmersdale CID, said: “Both staff members have been left shaken by their ordeals and we need to find the person responsible.
“We are urging anyone who recognises the offender to contact us immediately.”
Anyone with information can contact police on 101 with reference SC1702837.