International students' attitudes towards teachers' codeswitching to the first language (L1) have not been adequately investigated in cross-cultural English-medium instruction (EMI) settings, where teachers and international students do not share the same L1 while they interact in English as a lingua franca (ELF). To fill that void, this study investigated international postgraduate students from differing majors at a German university that has implemented EMI to enhance its global competitiveness. A questionnaire and semi-structured interviews were employed to measure the international students' attitudes towards German-native teachers' English-German codeswitching practices in EMI classrooms. The findings indicated that the participants generally held a negative view of codeswitching in EMI. Humanities students were more opposed to English-German codeswitching than STEM students. Local teachers' codeswitching was found to constrain the participants' academic integration and social participation in the university. Importantly, the participants were somewhat open-minded about codeswitching, but effective content delivery and an inclusive instructional space cannot be sacrificed. The findings of international students' multifaceted understandings of languages offer insights into teaching pedagogies, discipline-specific language policies and administrative support for EMI programmes.