“Brokeback Mountain” begins with two italicized paragraphs in present tense that feature the story’s protagonist, Ennis Del Mar, well after the story’s main events have taken place. Ennis, a middle-aged ranch hand, wakes before five in his trailer. The ranch’s owner has sold the place, and Ennis must move out this morning. He is unsure of what he will do, where he will go, or what his next job will be, but for now the uncertainty is assuaged by the pleasure of a dream he has just had about a man named Jack Twist.
The story leaps backward in time, to the spring of 1963, when Ennis and Jack first meet at the trailer office of Wyoming’s Farm and Ranch Employment. The narration shifts into past tense, signaling the beginning of the narrative of which we have just glimpsed the ending. Jack and Ennis are teenagers, born and bred in opposite corners of Wyoming on poor ranches. Both are well acquainted with a life of hard work and rough living, and both are high school dropouts. Ennis lost both parents when he was young and grew up in the care of two older siblings. At age fourteen he received a hardship grant for a truck to drive to school, but the truck soon broke down and he went to work on a ranch. Now he is engaged to Alma Beers.
Jack and Ennis sign on to become sheep herder and camp tender, respectively, for a foreman, Joe Aguirre, whose livestock spend the summer on Brokeback Mountain. Jack has done this once before, but Ennis is new to the job. Aguirre instructs the herder to sleep with the sheep in a pup tent, armed but without a fire, to prevent coyotes from killing the animals. Jack and Ennis drink and talk in a bar, then head up the mountain and get to work. After Jack complains about the four-hour commute to get to the herd, the men switch roles: Ennis heads up the mountain while Jack prepares meals in the camp. When they are together, they talk, drink whiskey, and become friends.
The men move the sheep to graze in a farther field, increasing the distance between pasture and base camp. One cold night, after much talking and drinking, Ennis decides to remain in base camp rather than trek back to the herd. It’s freezing and Jack tells him to join him in his sleeping roll inside the warm tent. In the tent, Jack reaches for Ennis’s hand and pulls it to his groin, only to be roughly turned and entered from behind by Ennis—the first time Ennis has been with a man. The sex happens many times after that, but they deny their homosexuality.
During a surprise visit to the campsite, Joe Aguirre sees the men together through his binoculars. In August, the sheep get mixed up with a Chilean herd, and Ennis and the Chilean herder struggle to separate them. In late August, Aguirre calls the men and sheep down from the mountain and frowns as he pays Jack and Ennis, knowing that some of the sheep aren’t his. The two men say goodbye, each evasive about his plans for the next summer. Jack has a bruised jaw—Ennis had punched him the day before. They part ways as though they don’t care. Once Jack is out of sight, Ennis has to pull over because he is sick with grief.
Ennis marries Alma and has two girls, getting work as a wrangler and on a highway crew to support his family. Alma wants to live in town, but Ennis likes the impermanence of their remote apartment.
Four years pass. Jack sends Ennis a postcard saying he is coming to town, and Ennis replies with his address. When Jack arrives, Ennis runs to greet him. Alma steps outside and sees them kissing in front of their apartment, then quickly goes back inside. She comes out again when the men have separated, and Ennis introduces Jack to her. The men tell each other about the children they have. Jack has married a Texan girl, Lureen. The men go to a motel, where they have sex all night. The next day, they reminisce about their time on Brokeback and talk about their feelings. Ennis says he hasn’t slept with other men, and Jack lies and said he hasn’t either. Jack tells Ennis he thinks Aguirre knew what happened on the mountain. He tells Ennis he was surprised by the punch on the last day. Ennis says his brother used to punch him and that he finally punched his brother one day, taking him by surprise. Jack suggests they set up a ranch together. But Ennis tells Jack about the time his father took him, as a child, to see the mutilated body of a gay rancher. He says they just have to endure this separation.
A rift grows between Alma and Ennis, and she divorces him when their daughters are nine and seven. She remarries. At a Thanksgiving dinner, she confronts Ennis about his affair with Jack, and he storms out.
The two men continue to see each other occasionally, but they never return to Brokeback. They tell each other about their affairs with women. During one trip, Ennis tells Jack he won’t be able to see him until November, although they’d planned to meet in August. While Jack has his wife’s money and her inherited business to fall back on, Ennis lives paycheck to paycheck and can’t miss work. Jack admits he travels to Mexico for sex because Ennis can’t give him enough of a life. They argue, but nothing is resolved. Jack remembers a time on Brokeback when Ennis simply embraced him and stood with him by the fire.
Months later, a postcard Ennis has mailed to Jack is returned to him, stamped “DECEASED.” Ennis calls Lureen, and she says that Jack had an accident: he was changing a tire when it blew up, sending the rim into his face. Ennis thinks it was no accident and that men killed him with the tire iron. Lureen says Jack wanted to have his ashes interred in a place called Brokeback Mountain, but she didn’t know where it was, so she buried half the ashes and gave the rest to his parents. Ennis decides to visit Jack’s family in Lightning Flat, Wyoming.
Ennis is met by Jack’s mother and his disapproving father in their tiny, depressing ranch house. Mr. Twist says Jack had long spoken of coming home to Lightning Flat with Ennis to help run the ranch, but had recently begun talking of bringing home another man, a Texan, instead. His mother invites Ennis to see Jack’s room. In the closet Ennis discovers an old shirt of Jack’s, stained with Ennis’s blood, layered over a shirt of Ennis’s, from their Brokeback days. Jack’s father says he’s putting his son’s ashes in the family plot.
Ennis buys a postcard of Brokeback and tacks it to his trailer wall; he hangs the two shirts beneath it on a nail. Around this time, Jack begins to appear in Ennis’s dreams.