English Medium Instruction (EMI) has been widely implemented and the number of international students has increased sharply, resulting from Korean universities’ major efforts towards becoming more international. This preliminary study was aimed at how Korean lecturers (n= 30) and Korean students (n= 31) measured the intelligibility and comprehensibility of Chinese, Vietnamese, and Mongolian students’ (n= 9) English utterances. The Korean participants listened to speakers’ utterances for the purposes of the intelligibility check and reported words that they did not recognize; in order to measure comprehensibility, they indicated their degree of perceived understanding of each speaker’s verbalization on the 5-point Likert scale. The Korean lecturers and students both measured the Chinese utterances of intelligibility and comprehensibility as the highest, whilst the students statistically measured the Vietnamese utterances as the lowest. The correlation coefficient between intelligibility and comprehensibility showed a relatively low relationship of r= 0.401. The Korean lecturers and students reported that they had difficulty understanding unfamiliar accented English such as Vietnamese and Mongolian English, which somehow affected communication held within EMI. Large-scale research involving various factors affecting English intelligibility and comprehensibility should be conducted with various L1 backgrounds in EMI.