Despite the advancement of the conceptualisations of teacher assessment literacy, teachers' assessment practices remain relatively low due to misalignment between teachers' beliefs on assessment and principles of effective assessment practices. The current assessment reform in the Philippines has not gained significant traction despite the ongoing professional development programs focused on enhancing teacher assessment literacy. We argue that to change teachers' exam-dominated assessment practices towards a more student-centred approach, there is a need to explore teachers' beliefs in assessment. Hence, we developed a context-driven tool using both theoretical and empirical approaches that could measure this construct, and which the results could provide a stronger foundation for professional development program. Factor analyses extracted nine dimensions that describe teachers' assessment beliefs: assessment for professional learning, for motivation, for measurement, for planning, for engagement, for learning, for evaluation, for norm-referencing and for instructional accountability. Implications of findings for teacher professional development and practice are discussed.