George is a small, lean, and clever migrant worker traveling through California during the Great Depression. He acts as a devoted but often frustrated caretaker for his companion, Lennie. Despite his occasional complaints about the burden of companionship, George deeply values their bond and shares a sustaining dream of owning a small farm together.

Lennie is a physically imposing, powerful migrant worker with an intellectual disability that gives him a childlike innocence. He relies entirely on George for guidance and survival. Lennie loves petting soft things like mice, puppies, and velvet, but he struggles to control his immense physical strength.

Slim is the widely respected "prince of the ranch," a masterful mule driver possessing a natural, quiet authority. Unlike the other men who travel alone, Slim shows empathy and understanding toward George and Lennie's unique friendship. He is fair-minded, confident, and stands as the moral center among the ranch hands.

Curley is the ranch boss's hot-headed son. A former boxer, he is small in stature and aggressively overcompensates by picking fights with larger men to prove his dominance. He is newly married, intensely jealous, and constantly searching the ranch for his wife.

Candy is an aging "swamper" (handyman) who lost his right hand in a ranch accident. Accompanied everywhere by his elderly, half-blind sheepdog, he fears outliving his usefulness and being cast out by the boss. Desperate for security and belonging in his final years, he eagerly latches onto George and Lennie's dream of owning land.

Curley's Wife is the only woman on the ranch, rendering her deeply isolated among the male workforce. Strikingly dressed with red lips and manicured nails, she married Curley to escape her mother and a failed dream of Hollywood stardom. Her lonely attempts to seek conversation with the ranch hands earn her an unfair reputation as a flirtatious troublemaker.

Crooks is the lonely Black stable hand who suffers from a crooked spine caused by a horse kick. Segregated from the white workers due to the harsh racism of the era, he lives entirely alone in the harness room. His forced isolation has made him proud, defensive, and deeply cynical, though he secretly longs for human connection and equality.

Carlson is a powerful, big-stomached ranch hand who owns a prized Luger pistol. He is pragmatic, unsentimental, and completely lacking in empathy for the emotional attachments of others. He embodies the harsh, survival-focused mindset required of the typical Depression-era migrant worker.

Whit is a young laboring ranch hand whose slouched posture already shows the physical toll of his agricultural work. He represents the typical migrant worker of the time, fascinated by a former worker's published letter in a magazine and eager to spend his hard-earned wages at the local brothel on weekends.

The Boss is the owner of the Soledad ranch and Curley's father. He is a stern, suspicious man who struggles to understand George and Lennie's partnership, incorrectly assuming George is taking financial advantage of Lennie's intellectual disability.

Aunt Clara is Lennie's deceased relative who raised him from infancy. She used to give him mice to pet until he kept accidentally killing them. Her memory represents a time of stability in Lennie's life, and she serves as a lingering moral anchor in his conscience.