Radio and stage plays
Orson Welles adapted and starred in Heart of Darkness in a CBS Radio broadcast November 6, 1938, as part of his series, The Mercury Theatre on the Air. In 1939 Welles adapted the story for his first film for RKO Pictures, writing a screenplay with John Houseman. It was intended to be entirely filmed as a POV from Marlow's eyes. Welles even filmed a short presentation film illustrating his intent. It has been reported as lost to history. The project was never realized; one reason given was the loss of European markets after the outbreak of war. Welles hoped to still produce the film when he presented another radio adaptation of the story as his first program as producer-star of the CBS radio series This Is My Best. Welles scholar Bret Wood called the broadcast of March 13, 1945, "the closest representation of the film Welles might have made, crippled, of course, by the absence of the story's visual elements (which were so meticulously designed) and the half-hour length of the broadcast.":95, 153–156,136–137
In 1991, Australian author and playwright Larry Buttrose wrote and staged a theatrical production of Kurtz (based on Heart of Darkness) with the Crossroads Theatre Company, Sydney. The play was announced to be broadcast as a radio play to Australian radio audiences in August 2011 by the Vision Australia Radio Network, and also by the RPH – Radio Print Handicapped Network across Australia.
In 2011, an operatic adaptation by composer Tarik O'Regan and librettist Tom Phillips was premiered at the Linbury Theatre of the Royal Opera House in London. A suite for orchestra and narrator was subsequently extrapolated from it.
Film and television
The CBS television anthology Playhouse 90 aired a 90-minute loose adaptation in 1958. This version, written by Stewart Stern, uses the encounter between Marlow (Roddy McDowall) and Kurtz (Boris Karloff) as its final act, and adds a backstory in which Marlow had been Kurtz's adopted son. The cast includes Inga Swenson and Eartha Kitt.
The most famous adaptation is Francis Ford Coppola's 1979 motion picture Apocalypse Now, which moves the story from the Congo to Vietnam and Cambodia during the Vietnam War. In Apocalypse Now, Martin Sheen plays Captain Benjamin L. Willard, a U.S. Army Captain assigned to "terminate" the command of Colonel Walter E. Kurtz. Marlon Brando played Kurtz, in one of his most famous roles. A production documentary of the film, titled Hearts of Darkness: A Filmmaker's Apocalypse, exposed some of the major difficulties which director Coppola faced in seeing the movie through to completion. The difficulties that Coppola and his crew faced mirrored some of the themes of the book.
On March 13, 1993, TNT aired a new version of the story directed by Nicolas Roeg, starring Tim Roth as Marlow and John Malkovich as Kurtz.
The video game Far Cry 2, released on October 21, 2008, is a loose, modernized adaptation of Heart of Darkness. The player assumes the role of a mercenary operating in Africa whose task it is to kill an arms dealer, the elusive "Jackal". The last area of the game is called 'The Heart of Darkness'.
The video game Spec Ops: The Line, released on June 26, 2012, is a direct, modernized adaptation of Heart of Darkness. The character John Konrad, who replaces the character Kurtz, is a reference to the author of the novella.
Victoria II, a grand strategy game produced by Paradox Interactive, launched an expansion pack titled "Heart of Darkness" on April 16, 2013. In it they revamped the colonial system, and naval warfare. 
- "And at last, in its curved and imperceptible fall the sun sank low, and from glowing white changed to a dull red without rays and without heat, as if about to go out suddenly, stricken to death by the touch of that gloom brooding over a crowd of men"
- "We looked at the venerable stream not in the vivid flush of a short day that comes and departs for ever, but in the august light of abiding memories. (...) The tidal current runs to and fro in its unceasing service, crowded with memories of men and ships it had borne to the rest of home or o the battles of the sea"
- "the sun set; the dusk fell on the stream, and lights began to appear along the shore"
The novel Hearts of Darkness, by Paul Lawrence, moves the events of the novel to England in 1666. Marlow's journey into the jungle is reimagined as the journey of the narrator, Harry Lytle, and his friend Davy Dowling out of London and towards Shyam, a plague-stricken town that has descended into cruelty and barbarism loosely modelled on real-life Eyam. While Marlow must return to civilisation with Kurtz, Lytle and Dowling are searching for the spy James Josselin. Like Kurtz, Josselin's reputation is immense, and the protagonists are well-acquainted with his accomplishments by the time they finally meet him.
Poet Yedda Morrison's 2012 book Darkness erases Conrad's novella, "whiting out" his text so that only images of the natural world remain.
President Obama picked up this book at Small Business Saturday on 29 November 2014.
Animator and Filmmaker Sascha Ciezata adapted the narrative to subway rats in a post Hurricane New York City for his serialized animated series on Instagram. In this version the rat Marley must navigate the flooded subway tunnels to find the elusive Rat King, Kurtz.