This paper examines the critical concept of posthumanism through an analysis of William Bruce Cameron's novel A Dog's Purpose: A Novel For Humans (2010). Human-animal studies have the power to resist the supremacy of humanism. Thus, nonhuman animals are seen as a key participant in a challenge to humanism. They are also displayed as being the victims of anthropocentric humanism. Adopting an analytical approach, this paper is divided into two parts: theoretical and practical. Theoretically, posthumanism challenges the anthropocentric view of the world by decentering the human and acknowledging the agency and subjectivity of non-human beings, particularly animals. Practically, by focusing on the human-animal relations depicted in A Dog's Purpose, this study aims to explore how the novel disrupts traditional notions of human exceptionalism and highlights the interconnectedness between humans and animals. Through a posthuman lens, the paper investigates themes such as animal consciousness, empathy, and the ethical implications of human-animal interactions. Human-animal studies have the power to resist the supremacy of humanism.