The benefits of quality early childhood experiences are indisputable as more studies have demonstrated the positive results of high-quality early childhood care and education (ECCE) on child outcomes. These benefits have recently spurred many countries to prioritise preschool programmes in their national plans and pursue a quality preschool agenda. This systematic literature review (SLR) aimed to analyse the worldwide practice of policy implementation regarding public preschool structural quality and examine the related challenges. This paper was based solely on SLR, where the literature was examined via the Scopus and Web of Science databases and Google Scholar. The review adopted PRISMA Statement (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and thematic analysis was employed to analyse the relevant research papers. The SLR revealed that varying service quality was the main theme of global public preschool policy implementation. In many countries in the included articles, the preschool education programmes were conducted by multiple agencies, which resulted in varied quality of the service provided. In this study, the analysis revealed five main themes: wide-ranging policy aims, combined public and private funding, complex governance and management systems with mixed national and state involvement, persistent fragmented structural and organisational aspects between ECCE and primary schooling, and varied ECCE service regulation and quality assurance. Thus, future research is necessary to bridge the knowledge gap to examine policy implementation of structural quality, specifically in individual country settings.