This case study focuses on mentor group conversation meetings with primary student-teachers, demonstrating how student-teachers ́ reflections on classroom experiences might influence their understanding of the complicated relationship between teaching, subject matter content and the context. The aim is to study how mentors ́ and student-teachers ́ reflections affect (or not) the student-teachers ́ development of pedagogical content knowledge (PCK). The theoretical framework derives from a sociocultural perspective, emphasising the collective character of teaching and learning. The empirical material consists of video documented mentor group conversations during one semester within an academic school context. Findings show development of PCK, highlighting a transition from pedagogical knowledge and contextual knowledge, to a blending of subject matter knowledge, pedagogical knowledge and contextual knowledge. This blending only occurred when the student teachers reflected on their teaching. Findings demonstrate the need to systematically explore student-teacher reflections of their teaching in practice to discern how different knowledge bases integrate into PCK. ©2019 The authors and IJLTER.ORG. All rights reserved.