Characters

George Milton – protagonist; a quick-witted man who is friends with Lennie. He looks after Lennie and dreams of a better life.

Lennie Small – protagonist; A mentally disabled man who travels with George. He dreams of "living off the fatta' the lan'" and being able to tend to rabbits.
Despite possessing a child's mental ability he is described as having strength like a "bull".

Candy – A ranch worker who lost a hand in an accident and is near the end of his useful life on the ranch. He wishes to join Lennie and George in their "dream" of a homestead.
Candy's dog – is described as "old" and "crippled", and is killed by Carlson. Candy's dog foreshadows Lennie's fate.

Curley – The boss's son – a young, pugnacious character, once a semi-professional boxer. He is very jealous and protective of his wife and immediately develops hatred towards Lennie.

Curley's wife – A young, pretty, woman, who is mistrusted by her husband, Curley. The other characters refer to her only as "Curley's wife," and she is the only significant character in the novella without a name. She had dreams of becoming an actress, but has failed to achieve this due to her marriage with Curley. She was described by Candy as flirtatous towards all of the male workers on the ranch.

Slim – A "jerkline skinner", the main driver of a mule team. Slim is greatly respected by many of the characters and is the only character that Curley treats with respect.

Crooks – The only black ranch-hand. Like Candy, he is crippled: his nickname refers to a crooked back resulting from being kicked by a horse. He sleeps segregated from the other workers, and is embittered from discrimination.

Carlson – A ranch-hand, he kills Candy's dog with little sympathy. It is also a foreshadowing of George's final solution to Lenny's actions.

Whit – A ranch-hand.

The Boss – Curley's father, the owner of the ranch.

Aunt Clara – Lennie's Aunt, only mentioned in references to the past.