Brown Hill couple Lyn and John O'Brien described the discovery of 16-year-old Keeshound-German Shepherd Cross, Tess, in Haines St as a miracle.

The dog was dehydrated and in pain after four days without food, water and its arthritis medication.

Two builders found her lying by the side of the road and gave her a drink of water from a hard hat.

Mrs O'Brien said she would never forget the sound of her husband's voice on the phone when he knew Tess had been found.

"You should have heard his voice - it was happy and emotional," she said.

"When I saw her I was in tears and hugging her.

"I don't know how she survived; it's an absolute miracle," she said.

Mr and Mrs O'Brien had woken about 6.45am Christmas Day to find Tess was not in her usual place near the back door.

Tess was treated for dehydration, arthritis pain and an infected wound on her foot at the Ballarat Family Petcare Clinic.

Mrs O'Brien said it was likely the dog would make a full recovery.