The study reported in this article examined the dynamics of plurilingualism, ethnicity, and effectiveness in intercultural encounters among a sample of 221 participants from Chinese universities via an online questionnaire and a situational judgement test comprised of three scenarios involving plurilingual and intercultural encounters. It employed latent profile analysis to identify distinct profiles based on participants' plurilingualism, including how they used their languages, their exposure to linguistic diversity in oral interactions, and their experiences with plurilingualism in society, school, and university. The study also considered participants' ethnic backgrounds and self-reported intercultural effectiveness. The findings revealed two latent profiles characterised by notable differences in ethnic background, language proficiency, language use, and experiences of plurilingualism in society, school, and university. Additionally, the most consistent predictors of participants' behaviour in the three scenarios were their fluid language use and exposure to linguistic diversity during oral interactions.