Many novice teachers experience a "reality shock" during the transition from teacher education programs to the first years of teaching, due to the unpredictable and dynamic nature of authentic educational contexts. To better understand novice teachers in transition, research on teaching English to speakers of other languages (ESOL) has explored their shifting behaviors and beliefs during the first years of teaching. However, this line of research has rarely examined the transformation of professional identities of novice ESOL teachers in a comprehensive way that allows for a broader understanding of the reality shock from the teachers' own perspectives. In order to address this gap in the literature, this article reports on a 3-year longitudinal case study of the transformation of the professional identities of four Chinese ESOL teachers during the first years of teaching in K-12 schools in China. The article highlights how these novice teachers' professional identities changed from the initial imagined identities formed in the preservice stage to the practiced identities constructed in the novice stage. (Contains 6 footnotes.)