The aim of the research project was to consider whether theoretical underpinnings of the concept of differentiation would help a group of modern languages student teachers develop their understanding and practice of differentiation in the classroom. This was a small-scale inquiry with qualitative data collected from three sources: student teachers, mentors and the course tutor of a one-year initial teacher education programme. The focus of this article is on the student teacher data only, collected via their reflections and responses to specific set tasks. Key findings to date have revealed that: a Postgraduate Certificate in Education course structure based on a theoretical framework with a focus on student learning enabled student teachers to engage in a wide range of effective differentiation strategies; they adopted approaches to differentiation mainly involving different levels of ability; they focused on the individual needs of their learners and adopted an inclusive approach to differentiation. Recommendations include the use of a wide range of theoretical perspectives to support student teachers in making the links between theory and practice explicit; the use of directed reading of theoretical texts; and the adoption of a reimagined definition of differentiation.