Philip Philippovich Preobrazhensky
Philip Philippovich Preobrazhensky is a 60-year-old professor, known not only in Russia but also outside its borders. He is a famous Soviet scientist and intellectual, and he owns a luxurious seven-room flat in Moscow. He has some Menshevik sympathies and despises the proletariat, who he sees as an ill-mannered and poorly educated subclass struggling to overturn decency and rationality. He detests Shvonder, who he sees as intrusive into his sphere of influence, and he is well-connected and protected within and by the Soviet government on account of his fame. He is kind to Sharik as a dog, but when Sharik begins to act with Bolshevik tendencies and manners, the Professor becomes distant, pale, and inconsolable. He only returns to normal after Sharik reverts to his original canine form. Less seriously, the Professor loves Verdi's Aida and sings selections from it regularly, as well as the serenade from Don Juan.
Ivan Arnoldovich Bormenthal
Ivan Arnoldovich Bormenthal is a former student of Professor Preobrazhensky, but he currently works with the famous academic as an assistant. He is incredibly handsome, devoted to his job, and is the professor's faithful friend, following the same philosophies and abiding by the same decorum. He is more resolute than his senior colleague and can use his strength to solve some problems, which leads the Professor to dispatch him to deal with Sharik time and again.
Zina
Zina is a servant girl who cleans the apartment, brings meals, and even assists during some operations. Zina is very sensitive person, but sometimes behaves and reasons like someone more strong-willed. As the professor's chief helper, she is berated on a near constant basis by humanoid Sharik, and he even attempts to assault her once in the night.
Sharik (Dog)
The dog Sharik is the main character of the novel, and he narrates a great deal of the story. He is a male dog, approximately two years old and of indeterminate breed— though he has a white patch on muzzle that makes him suspect that he has Newfoundland ancestry. He is observant of people and their behavior, noticing the power dynamics and stakes of most interactions almost immediately. He is also versed in how to read, though backwards. After getting shelter, he serves as a guinea pig for one of the professor's experiments. Even after all of his misadventures as a human, however, when returned to canine form at the end of the novel, he remains steadfast in his admiration and love for the professor.
Poligraph Poligraphovich Sharikov
Poligraph Poligraphovich Sharikov is a human entity created as a result of Professor Preobrazhensky's experiment with Sharik. By transplanting the pituitary gland and testes of the 25-year-old man Klim Grigorievich Chugunkin—a criminal, alcoholic, and balalaika player—into Sharik's body, a short man of unpleasant appearance with immoral behavior, weak cognitive faculties, and Bolshevik sympathies is born. Eventually, he becomes an agent of the Soviet state who works with the purge section to rid the city of stray cats, turning their pelts into faux squirrel for the masses. He is returned to his canine origins at the end of the novel.
Darya Petrovna
Darya Petrovna is the gruff woman who serves as Professor Preobrazhensky's cook. She at first dislikes Sharik, but comes to accept his presence in the kitchen. She has a male caller at one point, and later when Poligraph Poligraphovich tries to assault her, she mentions that she was once married. We also learn that she is in love with Dr. Bormenthal, at one point even snatching his photo from the professor.
Shvonder
Shvonder is the head of the house committee in the building where Professor Preobrazhensky lives. He is a Bolshevik ideologue, and he constantly attempts to have the professor's property seized or have his wealth redistributed to benefit others. He befriends Polygraph Polygraphovich and gets him involved with the actions of the party, even going so far at one point as to co-sign Polygraph's accusation of Professor Preobrazhensky. This constantly backfires, however, because the professor has friends in high places in the Soviet establishment and always stays ahead of him. For example, when Shvonder comes to inquire after Polygraph at the novel's end, the professor avoids murder charges by presenting the newly restored Sharik, whom he conducted another procedure on only shortly before.
