This study explored the perceptions of professional identity among three English teachers from diverse academic disciplines at a Korean university. The teacher participants were chosen based on their diverse sociocultural and academic backgrounds that created a small yet diverse sample of cases. Furthermore, each of them possessed a minimum of 10 years of teaching experience. This extensive experience enabled them to engage in profound reflections regarding the development of their professional identities through the lens of these experiences. Taking a poststructuralist approach, we utilized semi-structured interviews, class observations, and course-related documents to delve into the professional identity formation process and the factors influencing their identity formation. Our findings underscore that professional identity construction is an intricate process, shaped by sociocultural and institutional dynamics. Specifically, two dominant factors emerged: the implications of "native speakerism" and the distinctions between tenure and non-tenure academic tracks. These insights contribute to a deeper understanding of professional identity complexities among English instructors in Korean higher education institutions.