This qualitative case study investigated why and how a teacher used his agency in curriculum-making. The study uses in-depth interviews, classroom observation, and teaching artefacts to understand the socio-cultural perspective on the interplay among agency, resources, schema, and structure. It finds that in this case, teacher agency was triggered by the perturbation resulting from a misalignment between the teacher's personal beliefs and the school's cultural schema. Strategies for reconciling were enacted through resource creation, cultural schema integration, negotiation for curriculum space, and researching. More attention is needed to understand how the perturbation emerged in the practices, the coupling relationships between resources and cultural schema, and the agency transformation.