<p>This study investigates the integration of spatial thinking into early childhood education through story-driven design activities and the use of a Lesson Study approach. Conducted in six Irish junior and senior infant classrooms across two schools with ten teachers, this research aimed to address the following research question: How can the Lesson Study approach support early childhood teachers in deepening their knowledge of their pupils, changing teaching practices, and impacting teacher self-efficacy, particularly in relation to spatial reasoning during story-based design activities? Qualitative data from classroom observations and teacher discussions indicate that teachers adapted their lesson strategies based on deeper insights into their students' spatial thinking. They improved the development of spatial design assignments and demonstrated enhanced self-efficacy in conducting spatialized design lessons. Lesson Study dynamics enhance teacher awareness related to design and technology projects, foster creative task identification, and challenge teacher perceptions. Our findings suggest that the Lesson Study processes implemented in this study could motivate teachers to integrate spatial thinking into their classrooms while still adhering to their curriculum. This approach effectively integrates spatial thinking into the curriculum, providing authentic design scenarios for pupils to develop spatial reasoning. These outcomes underscore the potential of Lesson Study for teacher professional development in early childhood spatial and design education.</p>