Teacher attrition is a perennial problem in many countries around the globe. With attrition especially pronounced amongst early career teachers, efforts to retain and sustain these teachers have highlighted the importance of effective mentoring and support programs within schools. However, less is known about the perceptions and experiences of graduates of initial teacher education (ITE) programs who choose not to enter the teacher profession, therefore not benefiting from such mentoring and support, and subsequently being lost to the profession, potentially forever. Therefore, this paper reports on a qualitative case study that investigated the reasons why one group of graduates from an ITE program in Hong Kong chose not to teach. Using in-depth interviews and grounded in a theory of teacher identity construction, the results reveal how the participants struggled to construct their preferred professional identities, in particular during a teaching practicum, and the role this played in their decision not to enter the teaching profession. Implications for how teacher educators can better support preservice teachers as they struggle to construct their professional identities are considered and suggestions for future research are discussed.