This chapter examines the preschool to primary school transition in Ireland, and the factors that have influenced policies and practices surrounding this transition over the last 25 years. The last quarter century in Ireland saw significant policy changes and advancements that directly and indirectly impacted the transition from preschool to primary school for children. This included the introduction of early childhood curriculum and quality frameworks, the expansion of universal preschool provision, a whole-of-government strategy to support children from birth through age six, and a new transition template to support administrative bridging practice amongst preschools, primary schools, and the home. The chapter provides an overview of the Irish early learning and childcare and primary school education systems, governing bodies, and current curriculum frameworks and major policy initiatives. This is followed by a critical review of the last quarter century of research, policy developments and practices supporting and informing the preschool to primary transition. Finally, the chapter explores the last 25 years of changes and challenges in school transition experiences of educators, children, and families and outlines principles for future school transition practice and research.