The study examined the effects of primary school teachers' professional development activities on differentiated instructional practices in classrooms and possibilities for elevating students' learning engagement. A mixed method with concurrent triangulation design was used. The samples were selected by using purposive, simple random, and stratified sampling techniques. The data were collected through questionnaires, interviews, observations, and document analysis. The data were analyzed by using different descriptive (mean and standard deviation), and inferential (independent sample t-test and one-way ANOVA) statistics, and thematic narration. The findings indicated that teacher professional learning contributed to the development of professional and pedagogical competencies required in classrooms although the objectives of differentiated instructional practices were not aligned with the learning outcomes of diverse learners. The practices of students' learning engagement were not empowered due to the lack of appropriately differentiated contents, process, products, resources, and learning environment to address the diverse learning needs of children in the classroom. Therefore, contextualisation, conceptualisation and adaptation of best differentiated pedagogical practices should be realised by giving ongoing professional development training through face-to-face interaction, online digital and E-learning for primary school teachers.