Gregor is the main character of the story. He works as a traveling salesman in order to provide money for his sister and parents. He wakes up one morning finding himself transformed into an insect. After the metamorphosis, Gregor becomes unable to work and is confined to his room for most of the remainder of the story. This prompts his family to begin working once again. Gregor is depicted as isolated from society and often misunderstands the true intentions of others.
The name "Gregor Samsa" appears to derive partly from literary works Kafka had read. A character in The Story of Young Renate Fuchs, by German-Jewish novelist Jakob Wassermann (1873–1934), is named Gregor Samassa. The Viennese author Leopold von Sacher-Masoch, whose sexual imagination gave rise to the idea of masochism, is also an influence. Sacher-Masoch wrote Venus in Furs (1870), a novel whose hero assumes the name Gregor at one point. A "Venus in furs" literally recurs in The Metamorphosis in the picture that Gregor Samsa has hung on his bedroom wall.
Grete is Gregor's younger sister, who becomes his caretaker after his metamorphosis. Initially Grete and Gregor have a close relationship, but this quickly fades. While Grete initially volunteers to feed him and clean his room, she grows increasingly impatient with the burden and begins to leave his room in disarray out of spite. Her initial decision to take care of Gregor may have come from a desire to contribute and be useful to the family, since she becomes angry and upset when the mother cleans his room, and it is made clear that Grete is disgusted by Gregor; she could not enter Gregor's room without opening the window first because of the nausea he caused her, and leaves without doing anything if Gregor is in plain sight. She plays the violin and dreams of going to the conservatory, a dream Gregor had intended to make happen; Gregor had planned on making the announcement on Christmas Day. To help provide an income for the family after Gregor's transformation, she starts working as a salesgirl. Grete is also the first to suggest getting rid of Gregor, which causes Gregor to plan his own death. At the end of the story, Grete's parents realize that she has become beautiful and full-figured and decide to consider finding her a husband.
Mr. Samsa is Gregor's father. After the metamorphosis, he is forced to return to work in order to support the family financially. His attitude towards his son is harsh; he regards the transformed Gregor with disgust and possibly even fear, and he attacks him on multiple occasions.
Mrs. Samsa is Grete and Gregor's mother. She is initially shocked at Gregor's transformation; however, she wants to enter his room. This proves too much for her, thus giving rise to a conflict between her maternal impulse and sympathy, and her fear and revulsion at Gregor's new form.
The Charwoman is an old lady who is employed by the Samsa family to help take care of their household duties. Apart from Grete and her father, she is the only person who is in close contact with Gregor. She is the one who notices that Gregor had died and disposes of his body.