The book begins with a prologue where an unnamed narrator declares that he is an “invisible man.” He clarifies that his invisibility is not something physical; rather, it stems from others’ refusal to acknowledge his existence. Hence, he has isolated himself underground, secretly drawing electricity from the Monopolated Light & Power Company. He burns 1,369 light bulbs while playing Louis Armstrong's “(What Did I Do to Be So) Black and Blue” on a phonograph. He explains that he has gone underground to write about his life.

The narrator recalls his life as a young man in America’s South in the late 1920s or early 1930s. He is a gifted speaker, and one day he is summoned to deliver a speech to a notable assembly of white dignitaries in his town. The men are impressed and reward him with a scholarship to an all-black college; however, they humiliate him by coercing him to participate in a “battle royal.” In this degrading spectacle, he and other young black men are blindfolded and compelled to fight in a boxing ring. Following the ordeal, the white men further degrade them by making them scramble over an electrified rug to grab counterfeit gold coins. At the end, he is given a briefcase, which carries the scholarship. That night, the narrator dreams that the scholarship reads the following: “Keep This Nigger-Boy Running.”

At college, one day, the narrator is asked to chauffeur Mr Norton, a wealthy white trustee, around the campus. While showing him around the campus, Norton meets Jim Trueblood, an impoverished black man who has committed incest with his own daughter. Norton is both horrified and titillated to hear his story, and he tells the narrator that he requires a “stimulant” to recover himself. The narrator escorts him to the Golden Day, a bar primarily frequented by black men. On that day, a group of mental patients is present in the bar. While the narrator tries to get a drink out for Norton, he is forced to bring Norton into the bar. A fight breaks out, and Norton loses consciousness. A patient, who was formerly a doctor, tends to him and admonishes both Norton and the narrator for their ignorance regarding racial dynamics.

Once they return to the college, Norton complains to Dr Bledsoe, the president of the black college. Dr Bledsoe rebukes the narrator, admonishing him for failing to present an idealized portrayal of black life to Norton and instead showing the underbelly of it. Consequently, the narrator is expelled from the college. He is, however, given seven letters of recommendation addressed to the college’s white trustees in New York City and directed to seek employment there. The narrator leaves for New York the next day.

While on the bus to New York, the narrator encounters the former doctor once again, who gives him advice that the narrator struggles to comprehend. When the narrator arrives at Harlem’s vibrant black community, he is excited, but his optimism is soon dampened by the harsh reality of his unsuccessful job search, despite the letters from Dr Bledsoe. Eventually, he meets young Emerson, who reveals the true nature of the letters—they were intended to deceive rather than assist him.

While the narrator is disheartened, he is given hope by Emerson, who suggests that there’s a job opportunity at Liberty Paints. The narrator is livid at Dr Bledose but accepts the offer and begins working under Lucius Brockway, an elderly black man in charge of the factory’s boiler room and basement. However, tensions arise when the narrator inadvertently stumbles upon a union meeting. This makes Brockway suspect that he is collaborating with the union, and he attacks him.

In the ensuing altercation, the narrator manages to subdue Brockway but suffers severe injuries as Brockway triggers an explosion in the basement. Hospitalized and subjected to brutal electric shock treatments by the factory’s doctors, the narrator is stripped of his identity; he even forgets his own name. However, their racism triggers him. The narrator is abruptly discharged from the hospital and dismissed from his job at the factory.

After leaving the hospital, the narrator collapses on the street, whereupon members of the black community save him and bring him to Mary, a kind woman who offers him shelter in Harlem. Grateful for her kindness, the narrator lives with Mary, who nurtures his connection to his black heritage. One day, when the narrator witnesses the unjust eviction of an elderly black couple, he delivers a fervent speech condemning the eviction, catching the attention of Brother Jack, a member of the Brotherhood, a political organization that aims to work for the socially oppressed. Brother Jack offers him a role as the spokesman of the organization, and while he is initially hesitant, the narrator accepts the role to repay Mary’s hospitality. However, joining the Brotherhood requires the narrator to adopt a new identity, sever ties with his past, and relocate to a new apartment.

Formally initiated into the Brotherhood at a gathering in the Chthonian Hotel, the narrator assumes responsibility for advancing the organization’s agenda in Harlem. Under the guidance of Brother Hambro, a white member of the group, the narrator receives training in rhetoric and meets some prominent figures, such as Tod Clifton, a charismatic black youth leader, and Ras the Exhorter, a black nationalist advocating for separatism. As the narrator rises to prominence within the Brotherhood, he faces internal challenges, including accusations of self-serving ambitions from Brother Wrestrum. While these allegations are being investigated, the narrator is reassigned to advocate for women’s rights. After giving a speech one evening, a white woman tries to fulfill her sexual fantasies involving black men by seducing the narrator.

Once he returns to Harlem, the narrator discovers that Clifton has vanished, along with several other black members who have grown disillusioned with the Brotherhood’s perceived betrayal of their community’s interests. The narrator meets Clifton selling the derogatory “Sambo” dolls (dolls that are built in the image of the lazy and obsequious slave) on the street without a permit. When white policemen confront Clifton, he is shot in front of the narrator and bystanders. The narrator organizes a funeral for Clifton and delivers a moving eulogy portraying him as a hero, rallying public support in Clifton’s memory. However, the unauthorized funeral incurs the wrath of the Brotherhood, particularly Brother Jack, who admonishes the narrator for his unilateral action. As a consequence of his actions, the narrator is sent to Brother Hambro for further indoctrination into the Brotherhood’s revised strategies in Harlem.

This infuriates the narrator, who seeks revenge on Jack and the Brotherhood. He reaches Harlem to find it engulfed in racial tensions. Ras, the black nationalist leader, chastises the Brotherhood for squandering the momentum from Clifton’s funeral. When Ras sends his men to beat up the narrator, he disguises himself to evade them. The narrator adopts a new persona by wearing dark glasses and a hat. However, he inadvertently assumes the identity of Rinehart, a mysterious figure embodying various roles within the community. As he navigates the streets, he encounters both confusion and intrigue, with many mistaking him for the elusive Rinehart.

The narrator visits Brother Hambro in search of explanations and with the intention of undermining the Brotherhood, only to become disillusioned by the group's disregard for Harlem and the black movement. The Brotherhood's manipulation and exploitation of people disturbs the narrator, who decides to gather confidential information about them while appearing to side with them. He decides to seduce a woman named Sybil, close to one of the party leaders, to obtain secret information about the group.

The narrator soon finds out that Sybil doesn’t have much information about the Brotherhood. She instead wants to act out her own disturbing fantasy of being raped by a black man. While he is in her apartment, the narrator receives an urgent call asking him to return to Harlem, where he is thrust into the midst of a violent riot incited by Ras. Amidst the chaos and destruction, the narrator becomes unwittingly involved in arson. While he tries to escape, he encounters Ras—dressed as an African chieftain—who calls for the narrator’s lynching. While he manages to escape Ras, the narrator faces suspicion from two policemen, who believe that his briefcase contains stolen goods. In his frantic escape, the narrator falls into a manhole, and the police cover the manhole.

Reflecting on his experiences, the narrator realizes the importance of embracing his individuality while maintaining his commitment to community responsibility. He resolves to emerge from the shadows of invisibility, prepared to confront the challenges of the world above. Thus, his story comes full circle, with his emergence from the underground symbolizing a newfound sense of self-awareness and purpose.