Differentiated instruction (DI) addresses academic diversity in order to maximise learning. Although it is theorised as both a philosophy and as a praxis of teaching, it is rarely measured as such. This study examines teacher profiles on differentiated instruction relating to their philosophy and self-reported praxis. The data stem from an exploratory study on differentiated instruction, which served the purpose of creating a valid instrument to measure teachers' philosophy and teaching approaches relating to academic differences in interests, readiness and learning profiles, namely the DI-Quest instrument. The results reveal three teacher profiles based on five DI-related factors. The patterns are almost identical in primary and in secondary education. Interestingly, if more frequent adaptations to students' differences in interests, readiness and learning profile are what differentiated instruction aims for, both philosophical factors (namely growth mindset and ethical compass oriented to students) need to be present. Lacking one of these factors, will have less adaptations as a consequence. This study displays the predictive power of teachers' philosophy about Differentiated Instruction for their daily classroom practices. Consequences for future research, professional development and teacher education are discussed in detail.