The mobility of teachers is a global phenomenon that has affected the education environment worldwide. This study examines the professional transition of immigrant teachers and finds that teacher professional vulnerability is a critical emotion in the complex process of professional transition. Using a qualitative inductive approach, this study reports on the professional transition experiences of ten teachers who migrated from Asia to Australia. Findings revealed that teachers' perceived teaching competence and interactions with students and colleagues are significant elements contributing to immigrant teachers' professional vulnerability during their professional transition. I conclude by discussing the resonance between our findings and previous studies, new emerging findings, implications, and recommendations.