The film is set in Moscow not long after the October Revolution. A complaining stray dog looks for food and shelter. A well-off and well-known surgeon and professor, Philipp Philippovich Preobrazhensky, happens to need a dog and, with a piece of sausage, lures the animal to his large apartment, used both for living and medical practice. The dog is named Sharik and well taken care of by the doctor's maids, but he still wonders why he is there. He finds out only too late that he is needed as a test animal. The doctor implants a pituitary gland and testicles of a recently-deceased alcoholic and petty criminal, Klim Chugunkin, into Sharik.

Sharik proceeds to become more and more human during the following days. After his transition to human is complete, it turns out that he inherited all the negative traits of the donor (bad manners, aggressiveness, use of profanity, heavy drinking), but he still hates cats. He picks for himself the absurd name Poligraf Poligrafovich Sharikov, starts working at the Moscow department for extermination of stray animals and associates himself with the new Bolshevist building administration, who strive to take away part of doctor's big apartment (an ongoing sub-plot of the film). Eventually, Sharikov turns life in the doctor's apartment into a nightmare by stealing money, breaking his furniture, flooding the apartment during a cat chase, etc.

Preobrazhensky and his friend and assistant, Dr. Bormental, see all of their efforts to reform Sharikov fail. Eventually the doctor learns that Sharikov has attempted to denounce him to the Soviet secret police. The doctor then demands for Sharikov to leave the apartment immediately for good. Sharikov angrily refuses and draws a revolver. An infuriated Bormental attacks Sharikov and, after a short but violent fight, subdues him. The doctor then chooses to reverse the procedure.

Sharikov turns back into a dog. As Sharik, he remembers little about what has happened to him but is not much concerned about that. To his content, he is left to live in the doctor's apartment.

This screen version of M. Bulgakov's novel is famous for its fidelity to the original text. Practically nothing was deleted in the adaptation. In a documentary about the film, the cinematographer recalls that when he asked the director for the script, Bortko simply gave him a magazine with the text of the novel. When the baffled cinematographer objected, the next day Bortko gave him the same text, but with descriptions of nature and other such details crossed out.^[2] There are however some differences between the novel and the film: some scenes in the film involving spiritualism, the prophetess in the circus, and a Soviet style christening ("Octobering") were taken from early short stories by Bulgakov, rather than the novel.^{[citation needed]}

• Awards at several domestic and international film festivals,^{[citation needed]} including Prix Italia (1989)^[3]
• Vasilyev Brothers State Prize of the RSFSR (1990)^[4]

• Dog's Heart, a 1976 joint Italian-German comedy film directed by Alberto Lattuada based on the novel

• Heart of a Dog at AllMovie
• Heart of a Dog at IMDb  
• Heart of a Dog at Rotten Tomatoes
• Secrets of Our Cinema. "Heart of a Dog", a June 29, 2016 TV programme episode about the film (video)