In globalized societies, people with different native languages increasingly communicate through English, and varieties of cultural and linguistic backgrounds among these native and non-native speakers of English create multicultural and multilinguistic interactions. Given this diversification of English-speaking settings, the importance of cross-cultural and intercultural communication has become a key issue. This study examines Japanese university students’ experiences related to English as a Foreign Language (EFL) classes at their junior high and high schools by investigating how they perceive Japan’s domestic diversity and understand the role of English within that context. Insufficient attention to domestic diversity may mislead EFL learners when they encounter their English interlocutors with different cultural and linguistic backgrounds because this misunderstanding can create prejudices about English speakers and may reproduce a racial/ethnic and linguistic hierarchy. Drawing on survey and interview results, this study suggests possible strategies for promoting successful intercultural communication through English and teaching English as a global language. Finally it emphasizes that both native and non-native speakers of English should understand the values attributed to the diverse varieties of the language.