Is the Swedish author Stig Dagerman an existentialist? This work takes a close look at Dagerman’s novel Island of the Doomed to see if it is possible to consider it an expression of existentialist thinking and to see if it interacts with any specific existentialist tradition. Dagerman’s novel was compared with select works of five existentialist thinkers – Søren Kierkegaard, Martin Heidegger, Jean-Paul Sartre, Albert Camus and Karl Jaspers, all read in the light of the four categories of existentialistic thinking identified by the Swedish scholar Lennart Koskinen. All the four categories appeared to be central themes within the novel and a few subcategories were identified. An analysis based on these subcategories showed that the novel had obvious similarities with all of the five existentialistic thinkers. The main conclusion of my work is thus: it is reasonable to consider Stig Dagerman’s novel Island of the Doomed an expression of existentialist thinking, but it doesn’t match any specific existentialist tradition. Dagerman is therefore to be considered an independent existentialist.