Hitchcock planned the film as a change of pace after his dark romantic thriller Vertigo a year earlier. In his book-length interview Hitchcock/Truffaut (1967) with François Truffaut, Hitchcock said that he wanted to do "something fun, light-hearted, and generally free of the symbolism permeating his other movies." Writer Ernest Lehman has also mocked those who look for symbolism in the film. Despite its popular appeal, the film is considered to be a masterpiece for its themes of deception, mistaken identity, and moral relativism in the Cold War era.
The title North by Northwest is a subject of debate. Many have seen it as having been taken from a line ("I am but mad north-north-west: when the wind is southerly I know a hawk from a handsaw") in Hamlet, a work also concerned with the shifty nature of reality. Hitchcock noted, in an interview with Peter Bogdanovich in 1963, "It's a fantasy. The whole film is epitomized in the title—there is no such thing as north-by-northwest on the compass." ("Northwest by north", however, is one of 32 points of the compass.) Lehman states that he used a working title for the film of "In a Northwesterly Direction," because the film's action was to begin in New York and climax in Alaska. Then the head of the story department at MGM suggested "North by Northwest," but this was still to be a working title. Other titles were considered, including "The Man on Lincoln's Nose," but "North by Northwest" was kept because, according to Lehman, "We never did find a [better] title." The Northwest Airlines reference in the film plays on the title.
The film's plot involves a "MacGuffin", a term popularized by Hitchcock: a physical object that everyone in the film is chasing but which has no deep relationship to the plot. Late in North by Northwest, it emerges that the spies are attempting to smuggle microfilm containing government secrets out of the country. They have been trying to kill Thornhill, who they believe to be the agent on their trail, 'George Kaplan'.
North by Northwest has been referred to as "the first James Bond film" due to its similarities with splashily colorful settings, secret agents, and an elegant, daring, wisecracking leading man opposite a sinister yet strangely charming villain. The crop duster scene inspired the helicopter chase in From Russia with Love.
The film's final shot—that of the train speeding into a tunnel during a romantic embrace onboard—is a famous bit of self-conscious Freudian symbolism reflecting Hitchcock's mischievous sense of humor. In the book Hitchcock / Truffaut (p. 107–108), Hitchcock called it a "phallic symbol... probably one of the most impudent shots I ever made."