This doctoral study investigates the impact of belonging to a Community of Practice (CoP) on post-primary teachers. The understanding of teacher professional learning (PL) as witnessing a transformative reform agenda stemming from recommendations from national and international reviews of existing teacher education teacher PL has also gained attention from the publication of Cosán’s Framework for Teachers’ Learning (2016) and the recent Action Plan (2021) to support its implementation, underpins this study. This investigation into belonging to a CoP in an increasingly demanding educational landscape is scaffolded by two key pillars: the impact on teacher professional learning and teachers' sense of belongingness. Firstly, teachers lead PL based on their own experiences, as continuous engagement and collective learning occur more frequently when teachers work together to develop their professional growth further CoPs offer a high-quality, job-embedded form of professional learning that has several benefits. Secondly, belongingness is a fundamental human need, and it is difficult for teachers to fulfil their duties and responsibilities fully without a high sense of belonging to their profession. Although teacher PL has its challenges (lack of motivation, lack of time and lack of appropriate learning opportunities), CoPs have a positive impact on members’ self-directed PL in building community, collaborating with colleagues, developing instructional practice and feelings of support and belonging. A constructivist paradigm informs this qualitative case study design. This study researched the experience of seven post-primary teachers in a school in the Leinster region through employing participant reflective journals and semi-structured interviews. Thematic analysis has shown three themes to emerge: CoPs for belonging and wellbeing, CoPs for PL and CoPs for teacher agency.