In 1975, Travis Bickle is a lonely, depressed 26-year-old living in isolation in New York City. Travis takes a job as a night shift taxi driver to cope with his chronic insomnia, driving passengers around the city’s boroughs. He frequents porn theaters and keeps a diary in which he consciously attempts to include aphorisms, such as “You’re only as healthy as you feel.”
Travis becomes infatuated with Betsy, a campaign volunteer for Senator and presidential candidate Charles Palantine. After watching her interact with fellow worker Tom through her window, Travis enters to volunteer as a pretext to talk to her, then takes her out for coffee. On a later date, he takes her to see a pornographic film, which offends her, and she goes home alone. His numerous attempts at reconciliation by sending flowers and apologizing over the phone are rebuffed, causing him to become embittered and convinced that she is exactly like the “cold” people he detests in the city. He finally confronts her at the campaign office, berating her before being kicked out by Tom.
Travis is disgusted by the sleaze, dysfunction, and prostitution that he witnesses throughout the city, and struggles to find meaning for his existence. His worldview is furthered when an adolescent prostitute and runaway, Iris, who uses the professional name “Easy,” enters his taxi, attempting to escape her pimp, Sport. Sport drags Iris from the taxi and throws Travis a crumpled $20 bill, which continually reminds Travis of her and the corruption that surrounds him. One evening, an unhinged racist passenger gloats to Travis of his intention to kill his adulterous wife and her black lover. Travis confides in fellow taxi driver Wizard about his thoughts, which are beginning to turn violent; however, Wizard assures him that he will be fine, leaving Travis to his own destructive path.
In attempting to find an outlet for his frustrations, Travis begins a program of intense physical training. A fellow taxi driver refers him to an illegal gun dealer, “Easy” Andy, from whom Travis buys four handguns. At home, Travis practices drawing his weapons, and builds a rig to allow him to hide and quickly deploy one of his guns from his sleeve. He also begins attending Palantine’s rallies to study their security. One night, Travis enters a convenience store seconds before a robber enters and holds the owner at gunpoint, leading Travis to fatally shoot the robber. To help him evade arrest, the store owner, an acquaintance of Travis, takes responsibility for the deed, claiming one of Travis’s guns as his own.
Travis seeks out Iris through Sport, and twice tries to convince her to stop prostituting herself, an effort which partially convinces her. After a breakfast with Iris, Travis mails her a letter containing money, imploring her to return home. Travis cuts his hair into a mohawk and attends a public rally, where he intends to assassinate Palantine. While attempting to pull out his gun, Secret Service agents notice Travis putting his hand inside his coat and chase him down. Travis, however, successfully escapes the scene.
That evening, Travis drives to Sport’s brothel in the East Village. After Sport flicks a cigarette at Travis and derides him outside of the building, he shoots Sport and enters the brothel. Travis shoots the owner’s fingers off before being shot in the neck by Sport, whom he fatally shoots in turn. Travis moves upstairs, pursued by the owner, where Iris’s client shoots him in the shoulder; Travis kills the made man with the sleeve pistol, stabs the gangster in the hand and fatally shoots him with the made man’s revolver as Iris cries out in terror. He attempts suicide with the revolver, only to find it empty; the police arrive and find a collapsed, bleeding Travis, who looks at them while pantomiming shooting himself before passing out from blood loss.
Travis is not prosecuted, but instead, he is hailed as a local hero in the press, as the criminal dealings of those in the brothel were discovered and publicized. He receives a letter from Iris’s father, thanking him for saving her and revealing that she has returned home to Pittsburgh, where she is going to school. After weeks of recovery and returning to work, Travis encounters Betsy as a fare. Travis drives her home, then refuses to let her pay the fare, driving away with a smile. As Travis drives off, he becomes suddenly agitated after noticing something in his rear-view mirror.