The objective of this study is to explore the process of professional identity construction of two English as a foreign language student-teachers from a sociocultural theoretical lens. A qualitative case study was conducted through personal narratives, semi-structured interviews, and a focus group. The data were analyzed using a grounded theory approach. The results show that the process of student teachers' professional identity construction is unstable and dynamic, and is shaped by inter-related personal and external factors such as self-image, learning environment, and practicum experiences.