Using "pedagogical design capacity" ("PDC") as the conceptual framework, this single-case study examines how an English teacher in Hong Kong perceives and mobilizes curriculum materials to teach reading comprehension to secondary one students in two stages of implementation. Relying on data collected from semi-structured interviews, lesson observations, and analysis of curriculum materials, the study sought to uncover the underlying teacher knowledge at work when the teacher interacts with the curriculum materials. The findings show that knowledge of curriculum materials, personal practical knowledge, and knowledge of learners play an important role in making teachers more adept at using curriculum materials. Ultimately, the paper concludes with implications both theoretical and practical: The expansion of PDC framework and support to English teachers' use of school-based curriculum materials.