A Good Samaritan is spending the night in hospital after rushing to the aid of a dog owner whose pet was being attacked in Sydney.

Doug Hall suffered puncture wounds to his arms, which could also be fractured, but says if he didn't help the smaller dog would have been killed.

As he was led into the back of an ambulance, he says it could have been a lot worse.

View photos Doug Hall intervened in the dog attack. Source: 7 News More

View photos Mr Hall had bite marks and scratches. Source: 7 News More

"I'm alright, I'm just tired," Mr Hall said. "I'll be right, a bit sore."

Early Tuesday morning, Mr Hall was driving past The Avenue at Granville when he noticed a large dog attacking a smaller dog and its owner.

Without hesitation, he intervened, saving the pet's life, and will have the scars to prove it.

"I just pulled it away," Mr Hall said.

Doctors treated the 64-year-old in Westmead Hospital this afternoon. His injuries were severe enough that he'll be spending the night there.

"It's very sore, still very sore, can I move me fingers," he said.

Mr Hall said that on Friday he's supposed to walk a mate's dog for him while he's at work, but the incident has left him so traumatised, he doesn't think he has the confidence to do so.

View photos The bigger dog was taken by council officers. Source: 7 News More

"I could see that dog being ripped apart there," he said.

NSW Ambulance paramedic Craig Watkins said Mr Hall's actions were nothing short of heroic.

"There's no doubt he's a hero an Aussie legend he's jumped out of his car to help just an unknown person," he said.

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