Positive Behaviour for Learning (PBL) is a proactive and preventative approach for teaching appropriate behaviour in the school setting to promote positive academic and social performance. The PBL approach is based on the Positive Behaviour Intervention and Support (PBIS) model from the United States of America (www.pbis.org) and in 2005 was initially introduced to schools in the geographical region of South Western Sydney, New South Wales, Australia. This study investigated parent involvement in PBL in two primary schools in South Western Sydney. Research across many decades has demonstrated that parents have a significant influence on the behaviour, academic performance and school attendance levels of their children (Alvarez-Valdivia et al., 2013; Bowlby, 1951; Bronfenbrenner, 1979; Christenson & Hurley, 1997; Cooper & Crosnoe, 2007; Henderson & Mapp, 2002; Monti, Pomerantz & Roisman, 2014; Vincent & Tomlinson, 1997). Accordingly, the NSW Department of Education (NSW DoE) policies (NSW DET, 1996, 2006(a); NSW Education Act, 1990) and PBL literature (www.pbl.schools.nsw.edu.au) all emphasise the importance of parents, as partners with teachers, in the shared responsibility of educating children. There is a deficiency of implementation guidelines, aligned to Department policies and PBL literature that promote parent involvement in schools. Furthermore, such guidelines may not provide the necessary flexibility to support parent involvement across all schools due to the variability of school systems and contexts. Therefore, the implementation of PBL into Australian schools in the twenty-first century to promote the positive social and academic performance of students, and the knowledge that parents are a significant influence on student performance, it is critical to investigate the role of parents in PBL. Parent participation in PBL could be a factor that contributes to the fidelity of PBL processes and the overall sustainability of the positive behaviour systems. To date, there is a lack of Australian studies that have investigated parent involvement in PBL. Consequently, this study will contribute to Australian and international knowledge about parent involvement in PBL and, more widely, within schools. This study employed a qualitative methodology. The participants were teachers, parents and students from two South Western Sydney primary schools. The students were interviewed in focus group discussions, while the teachers and parents were interviewed according to their preference for an individual or group discussion. A semi-structured interview and the researcher’s reflective listening technique enabled participants to elaborate on particular themes which provided an in-depth understanding of parent involvement in PBL and more widely within the schools. Findings of the analysis showed that teachers believed parents had been involved in PBL implementation, however, the data showed that parents had gained knowledge about PBL vicariously through their children and not as a result of being involved in PBL implementation processes. The nature and extent of parent involvement were further explored more broadly within the two schools. Barriers to parent involvement and stakeholder perspectives to promote and improve parent involvement in general were identified.