Material development is one of the most important links in the chain of course design. However, it has received limited attention in the academic context of applied translation studies. This paper proposes a conceptual framework to encourage material development in interpreter and translator education at undergraduate levels. It first justifies the application of two idealistic principles (authenticity and diversity) to reflect market realism, thus narrowing the gap between classrooms and the professional world. For undergraduate T&I programmes, there seems to be an inherent conflict between the need to use diversified authentic texts and the fact that students are not yet competent enough to handle those texts. Classroom realism, for example, students' level and learning needs, should also be respected. The paper moves on to propose five additional principles (continuity in subject matter, simplification, scaffolding, building, and motivating), striking a balance between professional realism and classroom realism. As a demonstration, an undergraduate sight translation course is used to illustrate how each principle is followed in material development. This work is an attempt to inspire colleagues of translator and interpreter training to formulate their own material development principles that fit in with their teaching contexts.