A yellow cab emerges from the Stygian fog of the darkness of a New York City evening. Inside is the driver, Travis Bickle, his eyes alert for passengers to pick up and trouble to avoid. A quick flashback reveals most of what little personal information about Bickle’s background that we ever learn from the scene where showing him applying for the job. He is 26 years old, was honorably discharged from the Marines in 1973 at the peak of the Vietnam War before it finally began to wind up and, most important, he suffers from severe insomnia which causes him to ride around the city at night which leads him to the epiphany that if he’s going to being such a thing, he might as well get paid for it. And one last thing about Travis that is learned from the job interview: he’s got a clean conscience.
Seemingly coincident with starting his job as a hack, Travis also starts keeping a written journal, parts of which is narrative as voice-over observations while he is driving the taxi. The journal portrays a portrait of a lonely man becoming increasingly isolated within the most populous city in America. More than that: Travis is existentially aware of his loneliness and isolated. When he isn’t driving or writing, Travis goes to seedy theaters to watch porno flicks without exhibiting any obvious signs of actually be titillated. Sometimes he hangs out with the other cabbies at a 24 hour diner where he listens to an older and more experienced cabbie nicknamed Wizard dispense a mixture of advice and philosophy. Travis is never witness demonstrating any signs of comfort around other people, but he seems especially fidgety around blacks in the diner although he tries and fails to establish a romantic connection with a black woman operating concessions at the porno theater.
It is election season in America and inside the campaign offices of Senator Palantine who is making a bid for the White House is woman with hair the color of corn silk who looks more like a magazine model than a low level campaign staffer. Her name is Betsy and Travis develops an obsession with, parking outside the campaign’s headquarters just to stare at her. He also observes fellow staffer Tom daily making overtures to Betsy with his gift of dry humor and ironic self-awareness. Betsy takes notice of the cabbie who seems to show up every day and finagles Tom into checking him out, but as he approaches, Travis drives off.
Shortly thereafter, Travis has worked up the nerve to walk into the campaign offices and approach her. He asks to step out for coffee and Betsy is intrigued by his general sense of not being like the other guys who hit on her. They make a date and conversation over food, while uncomfortable, seems to draw them closer together. She agrees to go out to a movie with him.
Purely by coincidence, Travis later picks up Senator Palantine and his aide. Travis says he is the candidate’s biggest supporter, but when pressed to broaden his support, Travis resorts to far right rhetoric like that which fills his journal that focuses on taking action to “clean up” the city of the scum that takes it over at night.
The next far of the night is another blonde, but this one is barely a teenager and a prostitute. Her name is Iris and just as Travis is about to take off on her urgent order, a man reaches in, grabs her and pulls out. The man admonishes Travis to forget about the incident and tosses him a $20 bill as payment for rendering that particular service.
Travis arrives to take Betsy on the film date she agreed to, but she flinches when they show up the seedy Times Square theater. Travis convinces her that the film is popular with couples because that is what he actually and honestly believes. Inside, however, it doesn’t take long for Betsy to start thinking Travis is a creepy and worth keeping at a distance. She runs off and later Travis tries to talk to her to apologize. He even sends flowers to the campaign office, but they are refused. Finally, he angrily enters the campaign headquarters and confronts Betsy, but only winds up even angrier from the humiliation of being forced from the premises.
The journal entries reveal that Travis is on the verge of becoming completely alienated from other people. This alienation is exhibited in the form of illegally purchasing guns from an underground dealer, practicing at shooting ranges, rehearsing quick draws in front of the mirror, staring numbly at the television and what appears to be a rather benign means of stalking Palantine.
One night while buying stuff inside a convenience store, a young black thug tries to hold up the store. Travis uses one of his guns to shoot the thief. The owner tells Travis to go before the police arrive and as a result he faces no legal consequences for his actions. Meanwhile, Travis has been keeping a sharp eye out for Iris and eventually stumbles upon her one night. The man who pulled her out of the cab that first time turns out to be her pimp, named Sport. After a very awkward meeting with Sport, Travis finally manages to get Iris alone. She thinks he’s just another paying customer, but he rejects her come-on with revulsion. Their conversation reveals that Travis sees himself as her white knight, arriving to save her from the low place she has found herself. They agree to meet the next day for coffee. Iris admits to a dream of living in a commune in Vermont, but rejects Travis as her white knight. She thinks he’s just weird.
Travis shows up at a campaign rally for Senator Palantine sticking out like a sore thumb: he now sports a Mohawk. He moves closer to the stage as Palantine is speaking and reaches for his gun, but his appearance has already drawn the attention of the Secret Service and though they give chase, he manages to slip away. That opportunity foiled, he sets his designs on saving Iris instead. He shows up at the building where they met they met the other day, fully armed and loaded. In a violent and gory shootout, Travis manages to kill Sport, the owner of the room where Iris brings his customers and one of those customers. Travis is also shot and ravaged with his own blood as well as the others. The police arrive and Travis points a finger at his half-shaven head in a gesture of suicidal blowing out of his brains.
A few months later, Travis is back in his cab to the accompaniment of the sound of unfamiliar elderly man’s voice. He is the father of Iris and his words are the contents of the letter he wrote to Travis in thanks for returning his daughter to him and saving her from the hellish nightmare in which she was trapped. Meanwhile, newspaper headlines that reveal a narrative trajectory in which the violent shootout has transformed Travis in a heroic figure adorn his apartment. The last fare that Travis picks up before the film concludes is Betsy. She steps in, telling a silent Travis how she heard all about how he saved the young prostitute and how impressed she is by his actions. Travis merely stars at her reflection, never turning to face her or engage her in conversation before he lets her out and drives off into the night.