The year is 1895. Cattle baron and town patriarch George Washington "G.W." McLintock lives a solitary life on his ranch as a bachelor. His wife, Kate, left him without any explanation two years ago to embrace a life as a socialite back East, while their daughter, Rebecca "Becky", is away completing her college education. Although G.W. is well-liked by the locals, he faces opposition from the bureaucratic Matt Douglas and Governor Cuthbert H. Humphrey. G.W. maintains friendships with the community's sheriff, Lord, general store owner Jake Birnbaum, and even the local beggars and Comanche Indians.
G.W. issues a warning to some hopeful homesteaders about the land's unsuitability, noting it sits over 6000 feet above sea level. An earlier group had tried unsuccessfully to cultivate the area due to insufficient rainfall. Young Devlin "Dev" Warren, who has a family to support, approaches G.W. for work, but is initially turned away. Encouraged by the aging drifter Bunny, Dev resorts to begging, only to lash out in frustration when G.W. eventually agrees to give him a job. G.W. also hires Dev's widowed mother, Mrs. Warren, after enjoying her home-cooked meals. Just when things seem to settle, G.W. discovers that Kate has returned to town seeking a divorce in order to take Becky back East, but he firmly refuses. Kate, undeterred, decides to move back to the ranch, taking charge of everything, including the management of Mrs. Warren.
In a twist of fate, the Comanche tribe arrives in town to receive their chiefs back from prison, and Sheriff Lord positions them near the homesteaders. A misunderstanding arises when a homesteader's daughter elopes with her suitor, leading the townsfolk, including Douglas, to wrongly accuse the Comanche of kidnapping her. In a fit of rage, they attempt to lynch Running Buffalo, only to escalate into a brawl, with Kate defiantly siding with G.W.
Soon after, Becky returns from college, accompanied by Junior, the son of Douglas, whom G.W. disapproves of. Kate, however, feigns support for Junior. Along for the ride are four Comanche chiefs who have come to attend a hearing about their potential relocation to a reservation in Fort Sill, Oklahoma. G.W. agrees to advocate for them at the hearing.
As preparations for Becky's welcome-home party unfold, an argument sparks between Dev and Becky, when he labels Junior a "Dude." The tension escalates at the party, resulting in Dev stepping in to defend Birnbaum's assistant, Davy, during a fistfight, impressing the onlookers with his boxing prowess. The hostility between Dev and Becky grows when he accuses her of being a trollop after witnessing her kiss Junior. In a twist, Becky demands that G.W. punish Dev, leading to G.W. “shooting” him with a starter pistol as a lesson and allowing Dev to spank Becky with a coal shovel, much to Kate's dismay.
During the hearing, G.W. passionately presents a plea on behalf of his old rival, Paramount Chief Puma of the Comanche, only to be ignored by Governor Humphrey, who imposes their imprisonment until their relocation. That night, G.W., consumed by whiskey and frustration, suggests to Bunny that a show of resistance from the Comanche might bring attention to the Governor’s mismanagement. Returning home, he inebriates Mrs. Warren with drink; moments later, Kate witnesses them and misinterprets the situation, leading to further drama until Mrs. Warren clarifies her intentions of leaving to marry Sheriff Lord.
As the Fourth of July celebrations unfold the next day, Kate rebuffs Humphrey's advances but continues to clash with G.W. Meanwhile, encouraged by G.W.'s musings, Bunny aids the Comanche in their escape, arming them with Krag-Jorgensen rifles. They storm through town, pursued by the cavalry. In a unique hideout, Dev and Becky reconcile and become engaged. That entices G.W. to confront Kate, resulting in a heart-to-heart where she confesses her suspicions of infidelity which drove her away. Pursuing her through the town and making a bold statement with a public spanking, G.W. declares Kate free to pursue a divorce, yet she chooses to follow him, leading to a heartfelt reconciliation.
