William Gibb says he stopped at a Tim Hortons in Whitecourt, northwest of Edmonton, on Boxing Day.
He let his two dogs out for a bathroom break near a wooded area, then heard one of them crying in pain.
Gibb says he ran to see what was wrong and found the cougar on top of his husky, Sasha, so he bashed it with his fist.
The cougar jumped off and Gibb took the dog to a veterinarian, who stitched up her cuts and puncture wounds.
RCMP say they found the cougar in the trees near the restaurant and, because it was ready to pounce on officers, they shot and killed the animal.
Canadian man punches cougar attacking his dog near fast food restaurant
Canadian man punched a cougar in the face to stop it attacking his dog in a wooded area near a fast food store in Whitecourt, central Alberta, the Royal Canadian Mounted Police said on Wednesday.
William Gibb, 31, from Red Deer, Alberta, had stopped at a Tim Hortons outlet, a popular Canadian restaurant chain, while driving 372-miles to Grand Prairie on Monday evening and let his dog out for a walk, Tom Kalis, Whitecourt RCMP Sergeant, said.
Shortly afterwards, Mr Gibb heard his 80-pound female Husky called Sasha whimpering in pain and found a cougar pinning her to the ground.
"I could see something wrapped around her and wasn't sure what it was. I ran over and punched it in what I thought was the head, and it backed off and I realised it was a cougar," Mr Gibb, an electrician, said.
"I stepped over Sasha and charged at it swinging and screaming and calling for my brother and buddy to give a hand," he added.
Mr Gibb kept the cougar at bay, which he said swiped at him a few times, as he tended to his injured dog and called the police, before getting Sasha into his truck and driving her away for medical attention.
He said the police arrived five or 10 minutes later and, after consulting with fish and wildlife officers, killed the cougar because of the risk it could attack another dog or even humans.
Mr Gibb himself was not seriously injured, although Sasha bit him on the hand as he was trying to rescue her.
Mr Kalis said cougar sightings were not uncommon around Whitecourt because the town is surrounded by forests, but it is unusual for them to attack dogs.
In 2010, a Canadian family's golden retriever saved its 11-year-old owner's life when the boy was charged by a cougar in British Columbia.
The latest incident was reminiscent of an incident in Australia earlier this year when a hunter punched a kangaroo in the head to save a dog.
Greig Tonkins, an employee at Taronga Western Plains Zoo, ran towards an aggressive kangaroo that had his dog Max in a headlock during the incident filmed in June and which went viral this month.
Seconds after the kangaroo released the dog from a headlock, Mr Tonkins punched it in the face.
Canadian man punches cougar attacking his dog outside a Tim Hortons
Remember earlier this month when the most quintessentially Australian video ever went viral?
Well, get ready for some wild deja vu, because this is officially the most Canadian thing you will read this year, maybe ever.
On December 26 -- yes, Boxing Day -- a Canadian man put bravery before wit when he punched a cougar to stop it from attacking his dog, according to Reuters.
The hero in question, 31-year-old William Gibb from Red Deer, Alberta, had reportedly stopped on his way to work at a Tim Hortons outlet, a popular Canadian fast-food chain, to let his dogs out for a bathroom break.
Shortly thereafter, Gibb heard his 80-pound Husky Sasha whimpering in pain, and after venturing into a nearby wooded area to check on her, his worst fears were confirmed.
Gibb saw his beloved dog, helplessly pinned down underneath a large cougar.
So what did he do? He literally clobbered the massive jungle animal.
"He punched the cougar, yelled at it and got it to release the dog," the Royal Canadian Mounted Police (RCMP) Sergeant Tom Kalis told Reuters. "Then he called the police. He was quite lucky."
Sasha reportedly needed some medical attention but Gibb was not seriously injured, according to the RCMP.
"She's a tough one," Gibb told Global News Canada. "She's been pretty quiet, just recovering. It'll take her a few days to get back to her normal self."
Unfortunately, due to the cougar's close proximity to the popular establishment, and "because it was ready to pounce on officers," police shot and killed the animal upon arrival.