This paper aims to explore how Kazuo Ishiguro suggests the significance of communicative action and discourse ethics in his novel, The Remains of the Day based on the communicative action theory of Habermas. As Habermas clarifies communicative action and discourse ethics through mutual understanding, Ishiguro puts the emphasis on communicative action and discourse ethics with his narrative strategy through his main character. Stevens, the protagonist of the novel, serves as the first narrator but a unreliable narrator. He becomes the best communicator only when telling his story of private sphere and history of public sphere to the readers outside the novel. In contrast, he does not become an effective communicator in the novel. From this perspective, this paper attempts to postulate that Ishiguro implies the significance of communicative action and discourse ethics in light of the communicative action and discourse ethics by Harbermas. He tries to embody communicative action and discourse ethics in the public sphere by employing history as a technical device in the protagonist’s narrative. In addition, through the mechanism of memory, he defines Stevens as unreliable narrator and cowardice with the fear of expressing his emotion in spite of dignified and professional butler. At the end of the novel, Stevens’ personality develops further from a unreliable narrator and poor communicator to an effective and caring communicator. In conclusion, The Remains of the Day offers a philosophical insight on life and the significance of communicative action and discourse ethics through mutual understanding.