Higher Education (HE) institutions have incorporated online formative assessments as the integral part of teaching and learning. The literature points to a need for lecturers to have wide knowledge, including knowledge about student learning, domains of study, assessment and pedagogy, to effectively implement online formative assessment. The TPACK conceptual framework and the Revised Bloom’s Taxonomy (RBT) were used as a lens to interpret lecturers’ best practices in the implementation of online formative assessment. The study adopted a qualitative research using multiple case studies embedded with holistic cases. The purpose of the embedded case study was to investigate online formative assessment activities and document lecturers’ best practices when implementing online formative assessments at HE institutions in Namibia and Finland respectively. Therefore, three research questions guided the study which focused on assessment for learning: Firstly, to understand how online formative assessment is implemented at HE institutions. Secondly, to determine why do lecturers implement formative assessment in the online courses considering strategies and tools used for the designing and development of different types of formative assessment activities. Thirdly, identify what the challenges and benefits for online formative assessment at HE institutions. The results revealed that lecturers incorporated several tools to design and develop online formative assessment activities. In addition, lecturers demonstrated knowledge of TPACK which is considered a professional knowledge construct in the development of online formative assessment. Furthermore, the findings of this study indicated that lecturers provided feedback to students for all formative assessment activities. Lecturers had knowledge of identifying and addressing related challenges that could hinder the effective implementation of online formative assessment. The most noted challenges include poor internet connection, dishonesty on the part of students, insufficient time to provide immediate feedback for some assessment activities and lack of funding for research and innovation.