He was portrayed by Spike.
From the start, he is befriended and loved by Arliss Coates, but he is despised by his older brother, especially by stealing some of Travis' middling meat. One night, for this, Travis threatens to shoot him between the eyes if he takes one bite. So he doesn't.
Near the end, after having fathered puppies, one of whom is shown to be the title character of the next book and its film adaptation, Savage Sam, Travis is forced to shoot Old Yeller after he had been attacked by a wolf with rabies and tried to attack the family.
- When he had rabies, Old Yeller's growls and snarls were really recycled sound effects from Tramp, from Lady and the Tramp, when he was fighting the rat.
- The growls heard during Old Yeller's fight with the wolf would later be reused in One Hundred and One Dalmatians during Pongo and Perdita's fight against Jasper and Horace, and The Fox and the Hound when Copper was fighting the bear.
- Old Yeller's barks would later be reused for Chief from The Fox and the Hound, Nikki from Nikki, Wild Dog of the North, and Toby from The Great Mouse Detective.
- In the book, Old Yeller is a Blackmouth Cur, while in the film, he is a Mastador (Labrador Retriever/English Mastiff mix).
- In the book, he has a bobtail, while in the film, he has a long one.