Purpose: This research seeks to explore the potential of Lesson Study as a vehicle to support professional development (PD) in a rural, Irish primary school. Lesson Study was utilised to design and implement integrated STEM (Science, Technology, Engineering and Mathematics) lessons with young children (ages 4-7 years). Design/methodology/approach: Three teachers were introduced to and participated in four cycles of Lesson Study over the course of one school year. Qualitative data were generated from interviews, collaborative weekly meetings and observation sheets. Findings: Analysis suggests that Lesson Study supported the development of a culture of collaboration and provided an opportunity for teachers to share their knowledge. Findings also reveal that Lesson Study motivated teachers to reflect on their role within the classroom and enabled them to move away from teacher-led approaches. Although teachers perceived Lesson Study to be a beneficial form of PD, factors constrained their engagement, including practical, cultural and sustainability challenges. Practical implications: The study explores the adaptability of Lesson Study in first level education in the context of STEM education. It reveals teachers' first experience of Lesson Study, given its stark contrast to more "traditional" PD experiences they are accustomed to. This article will, therefore, be of interest to teachers, school leaders and policy makers. Originality/value: This paper contributes initial findings to a currently under-researched area, Lesson Study in a rural context. This study also combines Lesson Study with STEM education, which has not been widely explored.