Robert De Niro has said that despite having won an Oscar for Le Parrain, 2ᵉ partie (1974), he was still a relatively unfamiliar face, and was only recognized once while driving a New York cab during his research for this film.
Robert De Niro prepared for the role by working as a late night cab driver in New York City early 1975. One of his fares was a struggling actor who recognized him from Le Parrain, 2ᵉ partie (1974). The young actor said to De Niro discouragingly "Wait a minute, you just won an Oscar. My God... is it THAT hard to get work??"
Director Martin Scorsese claims that the most important shot in the movie is when Bickle is on the phone trying to get another date with Betsy. The camera moves to the side slowly and pans down the long, empty hallway next to Bickle, as if to suggest that the phone conversation is too painful and pathetic to bear; this shot also showcases his isolation and loneliness.
Robert De Niro worked fifteen hour days for a month driving cabs as preparation for this role. He also studied mental illness, and during his off-time when filming 1900 (1976), visited a US Army base in Northern Italy and tape-recorded conversations with Midwestern soldiers so that he could pick up their accent.
Between the time Robert De Niro signed a $35,000 contract to appear in this film, and when it began filming, he won the Oscar for his role in Le Parrain, 2ᵉ partie (1974), and his profile soared. The producers were worried that De Niro would ask for a deserved larger pay raise, since Columbia Pictures was very concerned about the project, and were looking for excuses to pull the plug on it, but De Niro said he would honor his original deal so the film would get made.
Victor Argo: As shopkeeper Melio who is held at gunpoint by a robber (Nat Grant), who is shot by Travis Bickle (Robert De Niro), thereby saving Melio.
Martin Scorsese: Sitting down, behind Betsy as she walks into the Palantine campaign headquarters in slow-motion.