This paper examines an under-researched area of teacher knowledge, namely teachers’ knowledge of materials use (TKMU). It aims to propose a conceptual framework to uncover the nature of TKMU by focusing on language teachers’ enactment of curriculum through the use of curriculum materials in higher education in Mainland China. As a burgeoning area of research in language education, particularly in applied linguistics (Tomlinson, 2012), materials use was currently defined as “the ways that participants in language learning environments actually employ and interact with materials” (Guerrettaz et al, 2018, p. 38). To use materials effectively, teachers must develop a robust knowledge with respect to materials use and the ability to mobilize a plethora of resources to engage students with the materials and thereby to promote students’ learning. Language materials (including curriculum materials) are ubiquitous and prevail in every classroom across the world (Tomlinson & Masuhara, 2018). Given the importance of language materials, there remains a large gap in the literature on how language teachers utilize materials to design and enact instruction and the knowledge recruited in this activity (Larsen-Freeman, 2014; Masumoto, 2019). By deploying Keller and Keller’s (1996) social learning theory of cognition in tool use and Shulman’s (1987) categorization of teacher knowledge, a qualitative multi-case study involving four Chinese English as a Foreign Language (EFL) teachers in one university in mainland China was designed to represent the study. Drawing on data from teachers’ pre-lesson and post-lesson interviews, lesson observations, and curriculum materials analysis in two successive semesters, language teachers’ six cognitive processes in materials use were generalized, namely, comprehending, conceiving, transforming, assessing, reflectingandreconceiving. The major constituents of TKMU that teachers recruited in each process were also unveiled. I propose that TKMU is a multi-dimensional construct, which is mainly manifest at four domains, i.e., subject matter, pedagogical, curricularandcontextual domains. This paper concludes that TKMU is mutually constitutive of teachers’ curriculum enactment, which provides room for teacher learning through informed reflection on the recurrent use of curriculum materials. Implications for in-service professional development and material development are also discussed.