Instructional materials are the tools used to educate learners and help the teaching-learning process be more effective and meaningful. However, teachers face problems regarding sources of information or materials to be used in instruction especially those teaching in public schools. Using a qualitative single-case study design, this study aims to determine the available instructional materials used by the Filipino Subject Teacher in a National High School which was identified by the City Division to be one of the low performing schools in the city based on the National Achievement Test 2016. This study will use purposive sampling and the use of semi-structured interviews as it links to Instructional Design Theory that worries how the student is going to learn and not more than what the student is going to learn. Results of this study could provide necessary assistance or school intervention for teachers teaching Filipino subject.