Unlike Mickey's other animal friends, such as Goofy (who is also a dog), Pluto is not a "funny animal". Pluto does not speak, walk upright, or wear clothing, but rather acts like a normal (if exaggerated) dog. A significant departure from this was his speaking role in The Moose Hunt (1931), which was produced before Pluto's characterization had been clearly defined. As Pluto made more appearances, it became common that he would not speak, but only vocalize in barks and grunts. Other ways of communicating Pluto's thoughts occur through his facial expressions, and sometimes through the use of a shoulder angel/devil who speak directly to Pluto.

Pluto is generally a cheerful and adventurous dog, although he can be given to sheer panic when confronted with something unknown. Common themes in Pluto's stories involve him becoming jealous of Mickey getting another pet, Pluto accidentally and unwittingly swallowing something and panicking when he realizes it, Pluto getting entangled with something inanimate, or Pluto being pestered by a smaller animal. In many of his appearances with Mickey, Pluto will get himself into trouble and cause Mickey to get angry at him. Mickey however, often cheers up quickly; often telling Pluto "I can't be mad at ya."Pluto sometimes appears with other regular animal characters. His friends include Fifi the Peke, Dinah the Dachshund, and Ronnie the St. Bernard Puppy. Other animals he is less friendly with include Salty the Seal, Butch the Bulldog, Figaro the Kitten, Chip 'n Dale, Spike the Bee, Ol' Benttail the Coyote, Milton the cat and other characters.