This article examines the influence of English language proficiency and intercultural competence on the English-medium instruction lecturer’s classroom leadership. It analyzes self-reported data obtained by three measuring scales from 188 English-medium instruction lecturers of a Chinese university. The Pearson correlational analysis indicated that there were significant positive relationships between the English-medium instruction lecturer’s classroom leadership and the two predicting factors. The multiple regression analysis suggested that both intercultural competence and English proficiency contribute much to the variance of the English-medium instruction lecturer’s classroom leadership. It was found that the lecturer’s language proficiency and intercultural communicative abilities could be two determining factors for the lecturer to deliver their disciplinary knowledge and command the class in an engaging and competent manner. The findings may provide implications for the strategic intervention of English-medium instruction educators in institutions of higher education.