The success of bilingual immersion programmes has promoted the debate about whether learners' first language (L1) should be used in foreign language classrooms. Nevertheless, Content and Language Integrated Learning, a pedagogical approach embedded in the development of multilingualism and multiliteracy theories, has overstepped the monolingual principle by allowing for more flexibility in the choice of instructional languages. Previous research has emphasised chiefly the reasons and effects of embracing a shared language, other than the target language, in content-based bilingual classrooms, while this paper intends to investigate the correlations between L1 use with learner factors, the understanding of which can shed light on more efficient translanguaging practices. Through a cross-sectional approach, the present study was contextualised in a large-scale, content-based English as a foreign language programme and drew on 335 undergraduates, who completed a series of questionnaires and tests. Correlation and regression analyses primarily demonstrated that English proficiency was the most significant predictor of learners' overall attitude to L1 instruction in classrooms, followed by content proficiency and language learning motivation. Gender was a non-significant variable for learners' overall perspective on L1 employment but was related to the constructs about using the L1 for phatic purposes, with male students requiring more translanguaging assistance. The paper concludes with the implication that the desire for L1 use is associated with various learner factors and that teachers should be aware of how to encourage and regulate translanguaging practices for differing instructional purposes as per the changing needs in classrooms.