Higher education institutions (HEIs) are seeking effective ways to address the rising demand for student mental health services. Peer support is widely considered a viable option to increase service capacity; however, there are no agreed definitions of peer support, making it difficult to establish its impact on student mental health and well-being.

This systematic review aims to better understand and evaluate peer support in HEIs.

Five databases, OpenGrey and Grey Matters were searched in May 2021. Included studies were quantitative, longitudinal (with and without a control) or cross-sectional with a control. The vote-counting method was used for synthesis. The risk of bias was assessed with the National Institutes of Health Quality Assessment Tool.

Three types of peer support were represented in 28 papers: peer-led support groups, peer mentoring and peer learning. Peer learning and peer mentoring had more positive, significant results reported for the outcomes of anxiety and stress. Peer-led support groups were the only type targeting students with mental health difficulties.

The heterogeneity of measures and outcomes prevents firm conclusions on the effectiveness of peer support for mental health and well-being. Most studies were rated ‘poor’ or ‘fair’ in their risk of bias. There is not a solid evidence base for the effectiveness of peer support. Nonetheless, HEIs can use the terminology developed in this review for shared discussions that guide more robust research and evaluation of peer support as an intervention.