This article reports a longitudinal case study examining how teachers were empowered to develop their professional capacity to cater for learner diversity through implementing differentiated instruction. Data were collected from multiple sources including lesson co-planning meetings, teacher interviews and lesson observations in a primary school in Hong Kong. The findings suggested a three-stage journey towards teacher empowerment mediated by both external and internal factors. The findings also highlighted the potential interplay of teacher empowerment, teacher professional development and its sustainability, shedding light on a sustainable model for teacher professional development.