Despite Rwanda’s national emphasis on play-based learning, classroom enactment remains uneven, with many preschool teachers relying on traditional, teacher-directed routines. This study examines how professional learning interactions and social participation shape teachers’ implementation of play-based pedagogy in Rwandan preschools. Using a convergent mixed-methods design, data were collected from 1,876 classroom observation points across 54 teachers and in-depth interviews with 10 purposively selected teachers. Quantitative analysis showed that 39% of all observed classroom actions reflected play-based principles, with the pedagogical domain scoring lowest (28.4%). Schools characterised by more robust collaborative routines: peer planning, feedback cycles, and leadership-supported reflection, demonstrated higher levels of child-centred practice. Qualitative findings revealed three distinct modes of professional participation: isolated enactment, where teachers work individually with minimal peer interaction; adaptive experimentation, where teachers attempt play-based strategies but without structured collegial support; and collaborative reflection, where collective inquiry consistently shapes classroom practice. Integrating Communities of Practice (CoP) theory, the study argues that sustained pedagogical change depends less on workshop-based training and more on the social infrastructures that enable teachers to learn with and from one another. The findings reconceptualise play-based implementation as a socially mediated process and offer practical implications for strengthening schoollevel professional learning systems in low-resource early childhood settings.