Although trained as an illustrator, Edward Hopper spent five years studying painting under Robert Henri, a member of the Ashcan School of painters who focused on the gritty realities of the city. The Ashcan School influenced Hopper’s style, though he tended to depict not the chaos of urban living but the sense of urban isolation. Hopper explained that Nighthawks was inspired by "a restaurant on New York’s Greenwich Avenue where two streets meet." The diner has since been destroyed, but the image, with its carefully constructed composition and lack of narrative, has a timeless quality that transcends any particular location. The painting reveals three customers lost in their own private thoughts. The anonymous and uncommunicative night owls seem as remote from the viewer as they are from one another. Although Hopper denied that he purposely infused any of his paintings with symbols of isolation and emptiness, he acknowledged of Nighthawks that, "unconsciously, probably, I was painting the loneliness of a large city."

In selecting his vantage point, Hopper eliminated any reference to the diner’s entrance. The viewer, drawn to the light shining from the interior, is shut out from the scene by a seamless wedge of glass, a characteristic of Art Deco design. Hopper’s understanding of the expressive possibilities of light playing upon the simplified shapes gives the painting its beauty. Fluorescent lights had just come into use in the early 1940s, and the eerie glow flooding the dark street corner may be attributed to this innovation. The moody contrast of light against dark and the air of menace inside has been linked to film noir, a movement in American cinema that featured stories of urban crime and moral corruption.