In minority language contexts, schools are constantly having to negotiate between the competing demands of minority language maintenance on the one hand, and the all-encompassing privilege of English in certain subject areas on the other. This dilemma is exacerbated in domains where English is seen to have a global tradition. Whilst the prevalence of English in STEM-related fields is well established, less is understood about the opportunities to study these subjects in languages other than English. Exploring the extent to which an English bias may influence pupils’ conscious choices around the study of STEM-related subjects, and how pupils negotiate the linguistic choice dilemma, can help inform school language policies and practices to better support pupils’ engagement with these subjects and to help address some of the limitations of a monolingual teaching approach for bilingual students. This study examined pupils’ likelihood of studying STEM-related subjects in Welsh-medium secondary schools in Wales, their linguistic choices around these subjects and their attitudes towards learning such subjects in English and/or in Welsh. The results revealed a general impression among pupils of the importance of English for STEM, which, mediated by their own linguistic backgrounds, abilities and experiences, influence pupils’ linguistic choices and desires to various extents, particularly at the latter stages of education. Since the propensity towards monolingual engagement with these subjects – in Welsh or in English – may limit the scope for scaffolding their learning across languages and the benefits that incur, we propose alternative bilingual approaches to STEM-related subject teaching.