The nature and significance of students' informal peer feedback networks is an under-explored area. This paper offers the findings of a longitudinal investigation of the informal peer feedback networks of a cohort of student teachers [n = 105] across the three years of a UK primary education degree programme. It tracked the dynamic nature of these networks through the use of Social Network Analysis and gained qualitative insights into the significance of informal peer feedback through diaries and interviews of a smaller student group [n = 12]. The research found that students were actively engaged in informal peer feedback networks from their first year of study. Where some students found strength within feedback 'cliques', others preferred the fluidity of relationships that were based upon identified needs and changing circumstances. The inter-connections between students' personal (ego) networks offered access to information flow across and beyond the cohort. Identified levels of informal peer feedback ranged from proof-reading aspects of assignment completion to the development of conceptual understanding that drew upon shared analysis of tutor feedback, assignment briefs and assessment criteria. While aspects of informal peer feedback built upon examples from tutor-led scenarios, trust and reciprocity were fundamental to the success of these informal peer feedback relationships.