In Heart of Darkness, Conrad doesn't explicitly tackle racism as a central theme, but it is depicted as the prevailing mindset of the time. The African natives are derogatorily referred to as "niggers," "cannibals," "criminals," and "savages." European colonizers regard them as an inferior race, subjecting them to chaining, starvation, theft, mutilation, and murder without fear of consequences. The book provides a harsh critique of imperialism by illustrating the white man's belief in his inherent right to invade and exploit lands inhabited by people of other races.

Kurtz is writing a document for an organization called the "International Society for the Suppression of Savage Customs," which hints at a global initiative to dominate all nonwhite races. He attributes a childlike quality to the Africans, suggesting that they perceive white people as supernatural beings. Indeed, the natives appear to have worshipped Kurtz as a deity, even offering human sacrifices to him. Kurtz considers their innocence a sign of inferior intellect and concludes that the solution to dealing with the natives is their complete extermination.

During the early part of his journey, Marlow observes a group of black men paddling boats. He admires their naturalness, strength, and vitality, feeling that they simply want to coexist with the land. This perception initially reassures him that he belongs to a world of reason. However, this feeling is short-lived. Marlow soon begins to view the Africans as less than human, using the derogatory language of his era to describe them as "creatures," "niggers," "cannibals," and "savages." He does not protest or intervene when witnessing six Africans forced to work with chains around their necks, describing the look in their eyes as the "deathlike indifference of unhappy savages." Marlow shows a trace of compassion by giving a dying young African one of the ship's biscuits. Although he mourns the death of his helmsman, he notes that the man was "a savage who was no more account than a grain of sand in a black Sahara." It's not the man he misses but his function as a steersman. Marlow refers to the "savage who was fireman" as "an improved specimen," comparing him, standing before his vertical boiler, to "a dog in a parody of breeches and a feather hat, walking on his hind legs."