This study longitudinally examined university-level students' stances, communication of negative emotions, and L2 swearing with regard to English-medium instruction (EMI). Sixteen graduate students enrolled in an English-medium course in a university in Korea participated in the study. The research instruments were classroom observations, reflective journal writing, and in-depth, semi-structured interviews. The results indicated that there were three occasions, during small group discussions, on each of which one student articulated her/his language ideologies against EMI and expressed her/his anger in Korean, and swore in English. These occasions occurred due to a student's opposition to EMI, a student's opposition to EMI preceded by her own support for it, and a student's opposition to EMI faced with another student's support for it, respectively. What affected the occasions included their teacher's idiosyncratic focus on general vocabulary in addition to subject-specific vocabulary (a factor common to these students), and challenges intrinsic to EMI, face, and the teacher's excessive academic push.