General Spielsdorf
At the beginning of the novella, General Spielsdorf is expected to visit Laura and her father with his niece, Bertha. However, these plans are cancelled when Bertha falls mysteriously ill and eventually dies. He grieves her greatly because he had loved her like a daughter. It is he who later visits Laura’s father and tells him the story that reveals Carmilla's true identity. He explains that a young woman named Millarca lived with them for three weeks and that it was during her stay that Bertha fell ill and died. He is convinced that Millarca is a vampire, and when he hears about Carmilla's relationship with Laura, he becomes convinced that Carmilla and Millarca are the same person. He goes with Laura’s father and Baron Vordenburg to the old cemetery in order to kill Carmilla once and for all.
Laura
Laura, currently 27 years old, narrates the story, recounting an event that happened when she was 19. She is kind, beautiful, and lonely. Her mother died in her infancy and she was raised by two governesses: Madame Perrodon and Mademoiselle De Lafontaine. She lives in a large, lonely house with only her father and the governesses. She has a close relationship with her father, frequently taking walks with him and describing him as "the kindest person." When Carmilla comes to stay with them, Laura is trusting of her and they become fast friends despite Carmilla's sometimes strange behavior. She is intensely attracted to Carmilla and suspects no ill of her, even as it becomes more and more clear that Carmilla has been preying upon her. Though she survives Carmilla's advances (barely, as she endures extreme weakness and lassitude), it appears she dies sometime between the telling of her narration and its publication.
Laura’s Father
Since Laura’s mother died when she was a child, her father raised her. He is an Englishman who was in the Austrian service, retired with a pension, and settled in an old feudal estate in Styria. He is a good-hearted man who willingly offers to let Carmilla stay at their estate when she appears sick after a carriage crash. He is also a practical man who does not initially think his daughter's illness could be due to supernatural causes. With the General and the Baron, he helps destroy Carmilla. After these events are concluded, he takes Laura on a trip to Italy in order to allow her to recover from the trauma.
Carmilla
Carmilla is a vampire of marvelous beauty. She is gentle and kind, her voice is soft, and she moves easily and elegantly. However, she has some strange tendencies, such as becoming agitated when she hears a funeral procession go by, not rising until one in the afternoon, and revealing nothing about who she is and where she came from. She appears to develop an obsession with Laura while staying at her home, acting very attentive and possessive of Laura.
Carmilla is only an anagram of her real name. She is actually Mircalla, the Countess Karnstein, who died many years ago. She had a lover and her early death plunged him into inconsolable grief. He moved her ruins to try and protect her, but she was then haunted by a demon who turned her into a vampire after her death. Her victims are young ladies. She visits them at night in the form of a huge black cat and leaves two fang marks in their chests. As a rule, her victims become ill and die, sometimes in days or weeks. She is finally killed in her grave with the help of General Spielsdorf and the Baron Vordenburg.
Bertha Rheinfeldt
Bertha is General Spielsdorf’s niece. Her parents died, so the General is her only family. Bertha is a beautiful young lady who is scheduled to come visit Laura at the beginning of the novella. We find out later from her uncle that she has died from a mysterious illness. She loved to dance, so they often went to balls. A victim of Carmilla's vampirism, she and her uncle met "Millarca," an anagram for Carmilla, and her mother at a ball. The mother asked the General to allow Millarca to stay with them for some time because she had some problems to solve. Millarca and Bertha became friends, but very soon Bertha fell ill and died. It became clear that it was due to Millarca, a vampire, though Bertha had no idea that there was anything afoul with her companion.
Carmilla's Mother
Carmilla's mother is described as an elegant, well-dressed older woman. She is very mysterious, and is the one who introduces Carmilla to her victims and then leaves. In the cases of both Bertha and Laura, Carmilla's mother leaves her daughter in the care of these young ladies' households, then departs, insisting on not revealing where she is going and what she is going to do.
Madame Perrodon and Madamoiselle De LaFontaine
They are Laura's governesses, who raised her and educated her in the absence of her late mother. They speak several different languages between them, and in Laura's narration she insinuates that they had little control over her since she was so spoiled by her kind father.
Baron Vordenburg
The Baron is a man who has dedicated his life to studying vampires. He knows about their history and how to kill them (by taking apart the body as it rests in its grave). He is the one who shares the information that allows Laura's father and General Spielsdorf to find Carmilla's grave and kill her permanently. He is descended from the Moravian nobleman, which is how he procured his information.
The Woodman
This man is chopping wood in the forest near Karnstein's ruins, and speaks with the General, Laura's father, and Laura about the problems that plagued that village.
Dr. Gratz
Dr. Gratz is the physician the General brings to the house to look into his niece's condition, and who informs him via letter that she is plagued by a vampire.
