This methodology paper presents how design-based research (DBR) can be used to prepare pre-service teachers (PSTs) to build their assessment for learning (A"f"L) literacy. A total of 335 PSTs involving 30 PSTs in the intervention group and 305 PSTs in the cohort group from one of the teacher training institutes in Myanmar participated in this study. The four phases of DBR, (1) problem analysis; (2) design and development; (3) testing and refinement; and (4) reflection to enhance the solution, were adopted. This paper highlights how each phase of DBR was used as a pedagogical approach to professional development in PSTs. The findings demonstrate the important contribution to teacher education of explicit teaching of A"f"L literacy using a specific professional development model.