This review aims to address a growing concern: Why are ethnic minority students, such as of Roma, bullied by their in-group peers for an ethnical reason? According to recent fndings, intra-ethnic bullying is becoming more prevalent across Europe; ethnic minority students are often bullied by one another more than by White-European peers. However, less is known about how intra-ethnic bullying happens in the same- or cross-ethnic minority groups and how it difers from inter-ethnic bullying. How classroom ethnic diversity afects not only inter-ethnic but also intra-ethnic bullying needs to be identifed for an accurate estimation of the prevalence rate, which appears inconsistent in the literature. This narrative review focused on common measurement methods leading to this inconsistency, provided theoretical explanations and proposed several hypotheses for further research. Prospective fndings might help to meet the growing concern for educational and social integration of ethnic minority students, particularly across Europe, Canada and the USA.