This book aims to investigate the theory and practice of EFL teachers' professional development in Benin. It explores theories such as sociocultural theory, activity theory, and reflective practice theory. Data were collected by means of two questionnaires administered respectively to EFL teachers and inspectors as well as content analysis. The findings revealed that teachers share valuable resources such as lesson plans, books, and audiovisual materials on social media. Further, they participate in professional development activities such as the weekly professional development workshops that provide the opportunity to discuss issues like assessment, activity planning and classroom management, as well as the zonal professional development workshops. Inspectors support EFL teachers through the organization of classroom observation visits and post-observation conferences, zonal professional development workshops, and assistance to teachers with special needs. The study recommends increasing the number of inspectors and diversifying professional development activities.