The social-belonging intervention is a wise psychological intervention designed to convey the message that worries and doubts about belonging during transition into higher education are common to all first-year students and tend to dissipate with time. The aim of this first systematic review on the social-belonging intervention was to investigate whether it can reduce achievement gaps in postsecondary education. Moreover, research questions about other outcomes possibly affected by this intervention and factors that may affect its efficacy were investigated. The protocol of this systematic review was registered with INPLASY. Four databases were searched for randomised control trials published in peer-reviewed journals testing the intervention in higher education. In total, 17 articles, which included a total of 21 studies, satisfied the inclusion and exclusion criteria as well as the quality assessment and were therefore included in this review. The reviewed research suggests that the intervention can narrow achievement gaps in higher education, as well as affect sense of belonging, academic fit, perception of adversities, use of campus support and the mental and physical health of disadvantaged students. These findings and their limitations, future research directions and recommendations are discussed in the final section.