Background: Despite the consensus regarding the value of school placement experiences for primary pre-service teachers (PSTs) in teacher education programmes, challenges remain in PSTs' ability to transfer the knowledge gained on assessment for learning (AfL) in their initial teacher education (ITE) programmes to the reality of the primary classroom. Furthermore, although there has been a significant growth of interest in assessment literacy and how this can impact teachers' use of AfL to enhance teaching and support student learning, there has been no research relating to primary PSTs' assessment literacy in enacting AfL in physical education. Purpose: The purpose of this study was to examine the extent that primary PSTs demonstrate assessment literacy in their enactment of AfL while teaching physical education during school placement. Methods: Participants included the teacher educator as researcher and four PSTs who were completing a two-year Professional Masters of Education in primary education to qualify as primary teachers. Using a longitudinal action research approach, the teacher educator generated data through participant observer field notes, primary PST reflective journals and individual primary PST interviews. The approach to data analysis involved data reduction, data display and conclusion drawing. Verification took place after each phase using inductive and deductive data analysis, thematic data analysis and constant comparative analysis. Findings: The use of teacher educator modelling, mentoring, and scaffolding with primary school students, during upskill sessions and in-situ during the PST school placements, enhanced the PSTs' assessment literacy in the enactment of AfL in primary physical education to a greater extent than when implemented during the module with their PST peers. However, while greater student autonomy, more effective planning, and connections between curriculum, pedagogy and assessment were evident, AfL strategies such as self- and peer-assessment were not as evident in PSTs' overall assessment literacy. Conclusions: The teacher educators' role in modelling and mentoring PSTs on school placement made a significant impact on PSTs' delivery of AfL. Based on the findings of this study, opportunities for PSTs to practice AfL with primary school students during the physical education module developed higher levels of assessment literacy for PSTs during school placement than was facilitated through theoretical discussion and content. This paper highlights the difficulties in developing PST critical engagement with assessment data and the rationale for PST reluctance around enacting self- and peer-assessment. While student relational dynamics could have impacted on this, it could be concluded that such AfL strategies require time to practice and develop. In addition, the duration of each block of school placement may not have facilitated PSTs with adequate time to implement peer and self-assessment.