The study investigated the beliefs expressed by a sample of 206 Polish and Spanish teacher-trainees about the use of learners’ native language (L1) in teaching English as a foreign language (EFL). Quantitative and qualitative data from a questionnaire revealed considerable differences between the two nationality groups in their beliefs about both medium-oriented and framework-oriented functions of the L1 in an L2 classroom. Moreover, significant differences were found in the participants’ accounts of their prior EFL learning experience in terms of the L1–L2 proportion in teachers’ classroom language use. A possible interpretation of these findings relates trainees’ beliefs to the L2 educational cultures prevalent in different countries, pointing to a contextually-mediated complexity of teacher-trainees’ belief systems. The study adds to the existing research on the issues underlying L1 use in L2 teaching that are currently under debate by offering a cross-national comparison of teacher-trainees’ beliefs about the place of the L1 in L2 instruction.