Travis Bickle is a 26-year-old honorably discharged U.S. Marine and Vietnam War veteran suffering from post-traumatic stress disorder and living alone in New York City. Travis takes a job as a night shift taxi driver to cope with his chronic insomnia and loneliness. He frequents the porn theaters on 42nd Street and keeps a diary in which he consciously attempts to include aphorisms, such as "you're only as healthy as you feel." He is disgusted with the crime and urban decay he witnesses, and dreams about ridding "the scum off the streets". Travis becomes infatuated with Betsy, a campaign volunteer for senator and presidential candidate Charles Palantine. Travis enters the campaign office where she works, and asks her out for coffee, to which she agrees. Betsy confesses that she feels a special connection to Travis, and agrees to go on another date with him. During their date Travis takes Betsy to a porn theater, which repulses her and causes her to leave. He attempts to reconcile with her, to no avail. Enraged, he storms into the campaign office where she works, and berates her before he is ordered to leave.
Experiencing an existential crisis and seeing various counts of prostitution throughout the city, Travis confides in fellow taxi driver nicknamed Wizard about his violent thoughts. However, Wizard dismisses them and assures him that he will be fine. In an attempt to find an outlet for his rage, Travis begins a program of intense physical training. A fellow taxi driver refers him to a black market gun dealer, "Easy" Andy, from whom Travis buys four handguns. At home, Travis practices drawing his weapons, and modifies one to allow him to hide and quickly deploy it from his sleeve. He also begins attending Palantine's rallies to scope out their security. One night, Travis shoots and kills a man attempting to rob a convenience store. On his trips around the city, Travis regularly encounters Iris, a child prostitute whom he fantasizes about saving. Travis solicits her and tries to persuade her to stop prostituting herself. Soon after, Travis cuts his hair into a mohawk and attends a public rally where he plans to assassinate Palantine. However, he is chased away by Secret Service agents who see him drawing his gun.
That evening, Travis drives to the brothel where Iris works, and shoots her pimp, Sport. He enters the building and engages in a shootout with Sport and one of Iris's clients, a mafioso. Travis is shot several times but manages to kill the two men. He then brawls with the bouncer, whom he manages to stab through the hand with his knife located in his shoe and finish him off with a gunshot to the head. Bloody and injured, Travis slumps on a couch next to a sobbing Iris. He attempts to commit suicide but is out of bullets. As police respond to the scene, a delirious Travis imitates shooting himself in the head using his finger. Travis goes into a coma due to his injuries. He is heralded by the press as a heroic vigilante and is not prosecuted for the murders, also receiving a letter from Iris's father, thanking him. After recovering, Travis returns to work, where he encounters Betsy as a fare; they interact cordially, with Betsy saying she followed his story in the newspapers. Travis drops her at home, and declines to take her money, driving off with a smile. However, Travis becomes suddenly agitated after noticing something in his rear-view mirror.
Robert De Niro as Travis Bickle
Jodie Foster as Iris Steensma
Cybill Shepherd as Betsy
Albert Brooks as Tom
Leonard Harris as Senator Charles Palantine
Peter Boyle as "Wizard"
Steven Prince as "Easy Andy", the Gun Salesman
Harvey Keitel as Matthew "Sport" Higgins
Martin Scorsese as the Deranged Passenger
Harry Northup as "Doughboy"
Victor Argo as Melio, the Bodega Clerk
Joe Spinell as the Personnel Officer