Ennis is a quiet, stoic 20-year-old ranch hand who grew up in poverty after his parents died in a car crash. Raised by his older siblings, he is accustomed to hard work and privation. He takes a job minding sheep on Brokeback Mountain to save money for his upcoming marriage to Alma. He is naturally reserved and practical. He remains highly sensitive to societal expectations.

Jack is a young, talkative cowboy who dreams of performing in rodeos. He comes from a poor background, having grown up on a struggling ranch with a harsh, unsupportive father. Assigned to sleep out on the mountain with the sheep, he chafes against the strict rules of his employment. Self-conscious about his appearance but eager for companionship, Jack actively seeks connection.

Alma is engaged to Ennis and desires a traditional home and emotional intimacy with her future husband. She embodies the conventional expectations placed upon young people in rural Wyoming. She quietly attempts to build a stable domestic life, though she notices details that complicate her understanding of her marriage.

Joe Aguirre is the pragmatic foreman who hires Ennis and Jack to mind sheep on Brokeback Mountain. He strictly enforces Forest Service rules, caring little for the comfort of his employees. He takes the young men's poverty for granted and silently observes them through binoculars during their employment.

Lureen is a woman from a wealthy background who marries Jack. Her family's money provides Jack with financial support, contrasting sharply with the poverty he experienced in his youth. Her father openly dislikes Jack, adding tension to their domestic life.

Earl is a man from Ennis's youth who lived with another man. His brutal fate serves as a violent cautionary tale that deeply affects Ennis's understanding of how society treats men who deviate from conventional expectations.

Jack's father is a former bullrider who lives on a meager ranch. He is a harsh and abusive figure who never offered Jack support or advice in his rodeo aspirations, leaving a lasting negative impact on his son.

Jack's mother lives in poverty on the family's small ranch, struggling alongside her husband to maintain their rural lifestyle.

Lureen's father is a financially successful man who provides his daughter with an income. He openly dislikes his son-in-law, creating a tense family dynamic.

Ennis's older brother takes on the responsibility of raising him when their parents die in a car crash. He inherits a heavily mortgaged ranch and struggles to keep the family afloat.

Ennis's older sister helps raise him after their parents are killed. She eventually marries and moves to Casper, leaving the struggling family ranch behind.

The two daughters of Ennis and Alma grow up in a conventional but emotionally strained household. They represent the family life Ennis attempts to maintain.

Jack's teenage son grows up with the financial support of his mother's family. He struggles to meet expectations, causing frustration for Jack.