This study was an attempt to investigate EFL teachers' professional development in an Egyptian school upon being engaged within a Professional Learning Community. The purpose of the study was to examine the impact of Professional Learning Communities on the targeted EFL teachers to find out its effect on developing their abilities of self-regulated teaching as well as on their professional identities. The study employed the case study design, focusing on EFL teachers who were teaching in an Egyptian national school. After being introduced and coached to the usage of Lesson Study as one of the strategies of Professional Learning Communities, these teachers were provided with daily reflection forms in order to internalize and reflect on their professional learning and development. Other instruments included observation grids, interviews, questionnaires, reflective memos, the researcher's log and documents review. Hence, mixed research methods were employed for triangulation purposes. Filling in the gaps in the available literature, and formulating a new framework for self-regulated teaching was the main contribution that this study strived to achieve.