Practitioner research is considered an integral form of professional learning for teachers but in its implementation it will often encounter significant challenges. This qualitative comparative case-study of teachers in Singapore and NSW investigated the range of challenges they encountered during their work as practitioner researchers. The study employs Schatzki's practice theory to analyse the impact of practitioner research on the existing practice architectures of schools. A total of 42 participants from NSW and Singapore were interviewed for this study. The results explicate the various challenges teachers encountered and how these act to prefigure and remodel practitioner research as a practice within each of the two different settings. The findings are of interest to teacher educators working with teachers across the career span who are considering using practitioner research in their professional learning repertoire.