Person-Environment fit (P-E fit), defined as the congruence between a student's attributes and their chosen study programme, is an important indicator of students' academic success (e.g. retention). Research has shown that students' informedness regarding the content and conditions of study before starting their studies is vital for this congruence. However, research on the factors that strengthen students' P-E fit after starting their studies is scarce. Students' peer networks could serve as a potential source of information, e.g. compensating for lower levels of informedness and thus, enhance students' P-E fit. Hence, this study investigates peer networks' moderating role, focusing on two types of P-E fit (Needs-Supplies and Demands-Abilities). Specifically, we examined how the composition of these networks (i.e. the proportion of informed peers) moderates the relationship between students' informedness at the beginning of their studies and their P-E fit perceptions three months later. Data were collected from 135 German university students. We identified the proportion of informed peers as a moderator between students' informedness and both P-E fit types. Practical implications for students and universities, as well as pathways for future research, are discussed.