BackgroundAlthough studies in China have found that school bullying is prevalent among adolescents, most relevant research has focused on southern China, while research in northern China is limited. This study aimed to explore ethnic disparities in the socio-demographic determinants of school bullying in Inner Mongolia, a northern region of China. MethodsA cross-sectional study was conducted among 2891 adolescents in Inner Mongolia, China, from September to December 2022. Data on participants' sociodemographic characteristics and school bullying experiences were collected through questionnaires. Multivariate logistic regression analyses, stratified by ethnicity, were employed to examine factors associated with school bullying. Furthermore, subgroup analyses and interaction tests were conducted to explore potential effect modifiers of the relationship between ethnicity and bullying. ResultsThe prevalence of school bullying was 18.99 % (549/2891) overall, with 17.96 % (420/2339) among Han and 23.37 % (129/552) among ethnic minorities. Minority adolescents faced a higher risk of bullying compared to Han (OR = 1.35, 95 % CI: 1.08–1.69, P < 0.05). Middle school students were more vulnerable to bullying than high school students (OR = 1.25, 95%CI:1.03–1.52, P < 0.05). Among Han adolescents, having a mother with high school education was protective against bullying (OR = 0.71, 95 % CI: 0.54–0.93, P < 0.05), while it was an associated factor for minorities (OR = 2.06, 95%CI:1.23–3.46, P < 0.05). Good family economic status was an associated factor for bullying among Han (OR = 1.62, 95%CI: 1.11–2.36, P < 0.05), but not among minorities. Belonging to other family structures (remarriage/foster family, intergenerational families, live with relatives and elders) was an associated factor for minorities (OR = 2.60, 95 % CI: 1.37–4.92, P < 0.05), but not for Han. Subgroup analyses revealed significant ethnic disparities in bullying experiences among middle school students, those from nuclear family, other family, and fair economic backgrounds (all P < 0.05). Interaction effects between ethnicity and these variables were not significant (all P > 0.05). LimitationsThis cross-sectional study has limitations in establishing causal relationships between identified associated factors and school bullying. ConclusionsEthnic minority adolescents in Inner Mongolia, China, especially middle school students, face a higher risk of school bullying than their Han peers. The differential impact of maternal education, family economic status, and family structure on bullying risk between Han and minority adolescents underscores the need for culturally sensitive, targeted interventions that consider the unique challenges faced by ethnic minority students.