This study examined perceptions of English as an International Language (EIL) by Korean English-major and non-English-major students. It also investigated factors that influenced their perceptions. The EIL Perception Scale was employed to assess two dimensions of EIL (i.e. varieties of English [VE] and strategies for multilingual/multicultural communication [SMC]) between English majors (N = 206) and non-majors (N = 172) in three separate regions of South Korea. Follow-up interviews were administered to 20 English and 20 non-English-major students for the purpose of delving into factors that might have influenced the differences in their EIL perceptions. Results showed that English majors held more positive perceptions toward both VE and SMC than did their non-English-major counterparts. It was also found that the differences in their EIL perceptions were mainly influenced by a teacher-structured EIL pedagogy and student-directed EIL experience in various informal digital learning of English (IDLE) environments. These results suggest that the EIL experience that occurs in a formal language classroom setting can positively influence students' EIL perceptions. Further, students' engagement in IDLE activities -- in which EIL teachers' instructional intervention is absent -- may also have a significant impact on their EIL perceptions.