In 1963, just outside Signal, Wyoming, hardened ranch foreman Joe Aguirre hires two nineteen-year-old farm boys to tend a large herd of sheep for the summer on Brokeback Mountain. Hard-working and coarse, Ennis Del Mar and Jack Twist are eager for the wages and the camping in open wilderness the job requires. Aguirre assigns Jack to tend the sheep, but demands that he tent beside the herd each night to protect them from predators. Further, he insists that Jack do so without a campfire, despite the cold temperatures, to avoid alerting the rangers, who require that the herders stay on designated campsites miles from the herd. Jack can return to the site for breakfast and dinner, made by Ennis, who is hired to cook and attend to weekly supply runs. The next day, Jack and Ennis get to know each other over a drink. Desperate to avoid farm work with his strict father, outgoing Jack earns his living riding rodeo bulls. The more reserved Ennis, orphaned at a young age, was reared by his sister and brother in poverty after the bank foreclosed on their farm. That afternoon, Jack and Ennis load the mules, saddle the horses and herd over a thousand sheep onto Brokeback Mountain’s vast pastures. In the first few weeks, the men settle into a routine with little communication. Ennis only reveals that he is marrying his sweetheart Alma in the fall, while Jack rants about the hours commuting between the herd and camp each day. On Ennis’ first supply rendezvous, a bear spooks the mules and horse, throwing him to the ground and causing him to search for hours for their supplies. Wounded, Ennis returns late to camp, where a concerned Jack tends to him. Later, Ennis, hoping to appease Jack, who is tired of canned beans, shoots an elk for meat and offers to camp with the sheep. As the days linger on, the intimate physical conditions of the camp and nightly whiskey drinking by the campfire open the men to teasing and talking. Jack proudly displays his rodeo belt buckle and admits his disappointment that his father, also a bull rider, never came to see him ride, while Ennis divulges that he was forced to quit high school to earn a living on his own and cares little for rodeoing, of which his father disapproved. Encouraged that Ennis has finally opened up, Jack mocks his own rodeo enthusiasm with bumbling antics and jokingly calls himself a “sinner” while explaining his Pentecostal upbringing, and a relaxed Ennis admits he is still a virgin. One night, Ennis, too drunk to return to the sheep, attempts to sleep by the campfire, but when it dies out, Jack orders the shivering man into his small tent. Late that night, Jack reaches for Ennis, who briefly resists but then draws Jack into a passionate kiss and the two have quick, rough sex. When Ennis returns to camp that evening after tending the sheep, he tells Jack that their night together was a “one shot thing.” Both quietly agree that they are not “queer” and continue their lovemaking that evening, more tenderly than before. The men continue to spend their nights together in the ensuing weeks, but after a snow storm hits the mountain, Aguirre, who has spotted the men in intimate horseplay through binoculars, orders them to bring the herd down early, claiming that more storms are expected. Jack tries to ease the tension by playfully lassoing his sullen lover, but Ennis is so overcome with unfamiliar emotions at the prospect of their summer ending that he violently punches Jack in the face. Having returned the herd to Aguirre, Ennis watches Jack’s truck pull away after a cursory farewell and is soon fighting back nausea and tears, unable to accept either his love for Jack or the end of their affair. The next summer, Jack returns to Aguirre after a year on the rodeo circuit, but the foreman hatefully berates him for “stemming the rose” with Ennis and refuses to rehire him. Meanwhile, Ennis works as a ranchhand and lives with his wife Alma and their two baby daughters, Alma, Jr. and Jenny, in a small apartment above a laundromat in Riverton, Wyoming. Resisting his longing for Jack, Ennis regularly pressures Alma into having anal sex despite her aversion to it and vents his frustration by picking fights with other men. In Texas, Jack marries self-assured barrel racer Lureen Newsome and works as a salesman for the Newsome farm equipment business, where he endures daily belittlement from Lureen’s father, L. D. Four years after his summer on Brokeback, Jack, having heard that Ennis lives in Riverton, sends a postcard there to arrange for them to meet when he drives through. On the appointed day, Ennis eagerly embraces and kisses Jack upon his arrival as a stunned Alma surreptitiously witnesses the scene. Claiming to Alma that he and Jack will be drinking all night, Ennis instead makes love to Jack at a hotel then returns home the next morning only to say that he is going on a weekend fishing trip, leaving Alma in utter despair. While camping, Jack speaks of ranching together, but Ennis stubbornly refuses anything but secretly meeting a few times a year. He then recounts his father’s vile warning: When Ennis was a child, he learned about ranchers Earl and Rich, who lived quietly together until other ranchers beat Earl to death to punish them for their homosexuality. Ennis’ father forced his two young sons to see Earl’s mutilated corpse, his penis torn from his body, as gruesome and haunting deterrent from the unacceptable behavior. Although sympathetic, Jack complains that every four years is not enough, but Ennis warns "If you can't fix it, you gotta stand it." Ennis and Jack then meet several times a year in Wyoming for their romantic camping trips under the pretext of “fishing,” enduring the long absences. Meanwhile Alma, unable to tolerate Ennis’ emotional distance and refusal to get a better paying job to support the family, divorces him and marries her boss, grocery store owner Monroe. Learning of Ennis’ divorce, Jack arrives unannounced in Riverton to spend an unscheduled weekend together, but Ennis claims that he must remain in Wyoming for the girls, who are visiting him that weekend. Heartbroken, Jack seeks solace by visiting a male prostitute in Mexico. On Thanksgiving, after dining with Alma, Monroe and the girls, Ennis, unable to admit his homosexuality, physically attacks Alma when she finally confronts him about his affair with “nasty Jack.” After he meets again with Jack, Ennis explains his growing paranoia that others can sense his homosexuality. When Jack suggests that he begin a new life in Texas, Ennis once again vehemently insists that he cannot leave because of his responsibilities. Soon after, Ennis begins dating saucy waitress Cassie and introduces her to the now teenage Alma, Jr., who bluntly states that her father will not marry again. Meanwhile, Jack, unknown to Ennis, continues to have love affairs with other closeted homosexuals. On one of their camping trips, Jack and Ennis, now in their thirties, share a marijuana joint and talk about their unsatisfactory lives. After Ennis informs him that they cannot meet again until November, not August as they had planned, Jack beseeches his lover to stop creating distance between them. Surmising that Jack is seeking sex elsewhere, Ennis jealously rages, blames Jack for his own homosexual behavior and finally weeps in Jack’s arms. While comforting Ennis, Jack remembers him as he was on Brokeback Mountain, when he relished their tenderness and was comfortable with their love. Later in Riverton, after Cassie tearfully confronts him for ceasing contact, Ennis, unable to tell her where his love really lies, offers her no explanation. Weeks later, Ennis’ postcard to Jack is returned with "deceased" stamped on it, prompting him to call Lureen for the first time. Lureen tells him that Jack died accidentally when he drowned in his own blood after a tire rim flew off and knocked him unconscious, but the shocked Ennis believes that Jack was beaten to death for his homosexuality. Learning that Jack wanted his ashes scattered at Brokeback Mountain, Ennis drives to the Twist family’s farm in Lightning Flat, Wyoming to carry out the request. Jack's father John's abhorrence of his deceased son is evident as he recounts that Jack had promised to take over the family farm with a divorced man he met recently. John then refuses to give Ennis the ashes, but Jack’s demure mother shows him to Jack's childhood room, where Ennis finds a shirt he had believed was lost on Brokeback, still stained with blood from their fight, hanging inside Jack's shirt. Cradling it, Ennis mourns his lover and returns to Jack's mother, who silently accepts Ennis' love for her son by offering him a bag to carry the memento. Sometime later, nineteen-year-old Alma, Jr. visits her father in his meager trailer to announce her upcoming marriage and leaves her jacket behind. As he gingerly places the jacket on his closet shelf, Ennis gazes at the two shirts, Jack's and his, hanging one inside the other next to a postcard of Brokeback Mountain, still longing to be with his first and only love.