This qualitative case study carried out at a Turkish university with four English language teachers aims to explore what teachers experience in the planning, implementation, analysis, and reporting phases of the lessons study process and what the implications of lesson study for teacher professional development can be. Data in this four-month study were gathered through observations, interviews, whole group discussions, and reflective reports. Findings revealed that lesson study had potential challenges and benefits for the professional development of teachers. The model poses challenges in finding a topic and research question, determining the lesson design and teaching style, making student thinking observable and analyzing qualitative data. On the other hand, it benefited teachers in terms of increasing their pedagogical content knowledge, reflectivity, research skills, collaboration, and collegiality. This study suggests that lesson study might be a good starting point for institutions wishing to adopt a more teacher-led, inquiry-driven and collaborative perspective for professional development.