Abstract Medical practitioners’ ethnocentrism and English language skills greatly influence intercultural communication in the context of health care. The present study sought to investigate the relationship between ethnocentrism and investment in learning English in multi-ethnic settings of English language classrooms at an Iranian medical university. To this end, the levels of ethnocentrism and investment in learning English of 200 Iranian medical students studying at Tehran University of Medical Sciences (TUMS) were measured using General Ethnocentrism scale (GENE) and Investment in English Language Learning scale.The findings of this study revealed a strong negative relationship between ethnocentrism and investment in learning English. In this study, the medical students’ levels of ethnocentrism and investment were relatively moderate, however, the results showed that female participants were less ethnocentric than their male counterparts were, but were not significantly different to them in terms of investment in learning English. Further, to provide a better understanding of the factors that contributed to these results, the relationship between various contextual factors and the participants’ ethnocentrism and investment were investigated. The findings revealed that more ethnocentric medical students tended to be from less ethnically diverse places, have fewer friends from other cultural backgrounds, get less exposed to English-speaking countries’ culture via internet, and believe their English professors and classrooms were from other ethnic backgrounds than themselves more often than less ethnocentric participants here. In addition, more ethnocentric medical students in the present study tended to modify their accent when speaking Persian less often, and felt less socially comfortable in their English classrooms. These students often believed that their resources were not valued in class compared to the less ethnocentric students. More ethnocentric students
