Differentiated instruction has been shown to meet the needs of diverse learners, and can meaningfully improve individual student learning, however many teachers find it challenging to implement. This paper reports on a targeted professional development programme which was undertaken as a collaborative action research project. Results show many participants adapted their classroom pedagogy to provide further supports for students through differentiated instruction. We argue that this study's use of a collaborative action research approach to provide teacher professional development, along with a focus on evidence using a differentiation observation instrument, were important stimuli for reflection and pedagogical experimentation. This targeted approach to professional reflection and exposure to research-based and other colleagues' teaching practices led to enhanced differentiated instruction among participants. These findings contribute to understanding the processes that lead to teacher development.