This chapter focuses on differentiation in English language teaching. We present the 5-dimensional (5D) model of differentiation which has been created based on the Finnish educational context. The model is grounded in the postulate that differentiation is a proactive and student-centred approach that permeates all teaching and involves the entire school community. The 5D model progresses from general to specific. It advocates for differentiation to be implemented holistically in several dimensions of teaching which are teaching arrangements, learning environment, teaching methods, support materials and assessment. Furthermore, it proposes that all differentiation should be based on students’ individual characteristics, such as learning profile, self-esteem, interests, readiness, needs, motivation, personality and history.