Objectives: The mental health of multicultural adolescents is an important social issue. We explored the differences in adolescents' mental health, including suicide modalities, between adolescents in multicultural and those in monocultural families. Methods: The results of 13th Korean Youth Risk Behavior Web-Based Survey (KYRBS) in 2017 were used. KYRBS is a cross-sectional survey, and the participants were drawn as stratified multistage clustered samples from 400 middle and 400 high schools in Korea. Student participation was voluntary and anonymous in this self-report, web-based survey. Results: Of the targeted 64991 adolescents, 62276 (response rate 95.8%) participated, and 58052 were finally included in this survey. The multicultural adolescents made up 1.56% of the participants, with female predominance and, compared with the monocultural adolescents, they were younger, shorter, and slenderer, and had lower parent educational status, lower self-recognized academic performance, lower economic status, and used smartphone longer time. Depressive mood was not statistically significantly higher, but suicidal ideation, plans, and attempts were higher in the multicultural adolescents. Daily smoking and drinking status, lower economic status, poorer self-recognized academic performance, and multicultural background itself, were positively related to suicidal attempts, and of these factors, the odds ratio was highest for a multicultural background, at 9.50. Conclusions: Multicultural adolescents tend to have much higher risk of suicidality problems. Therefore, more intensive education and practical prevention strategies are needed to reduce the suicidal behaviors of multicultural adolescents.