Trust is essential in any kind of peer-based mentoring. Taking a sociocultural view, this study focuses on how trust emerges relationally in a higher education context where colleagues observe and give feedback on one another's teaching. The term peer mentoring refers here to a collaborative approach in which faculty staff observe and give feedback on one another's teaching. The data in the study draw on video observations of and interviews with a four-member (senior faculty) peer group observed over a 5-month period. The analysis of the group interactions shows how the members made themselves vulnerable during peer review and reveals the implication of trust in this collaborative setting. The sociocultural perspective draws here attention to the key role of turn-taking rhythms in the interactions constituting the development of trust. This paper also discusses the significance of developing suitable conditions for trust when arranging peer-based review of teaching in higher education.