Teachers can be influential change agents in transforming their schools if they regularly reflect on their pedagogical practices, looking for improvements that will help all learners reach their full potential. However, in many sub-Saharan African countries, teachers seldom get an opportunity to collaboratively reflect on their practices. Action research, as an in-service professional development strategy, can be an ideal means of empowering teachers to collaboratively reflect on and improve their pedagogy to be more inclusive. Drawing from collaborative action research projects conducted by teachers in two primary schools in Zanzibar, Tanzania, this article explores the role of collaborative action research in developing the capacity of teachers to inform improvements in their pedagogical practices. The findings show how the participating teachers, with scaffolding influence from a critical friend (research facilitator), developed professionally along their zones of proximal development by promoting their pedagogical and research skills to enhance the presence, participation and achievement of all learners in their schools. Based on the findings, the article shows both the advantages and disadvantages of using collaborative action research in teacher professional development in the study context. The article also discusses the significance of organisational learning in in-service professional development in order to foster inclusive pedagogy through collaborative inquiry among teachers.