This article explores secondary English as a foreign language (EFL) teachers' differentiation practices in the Netherlands. We used the five-dimensional (5D) model of differentiation) as an analytical framework in the study. Additionally, we sought to identify the main challenges of differentiation in Dutch EFL teaching. We collected the data through a questionnaire (n = 52) and individual theme interviews (n = 3). We analyzed the quantitative data through descriptive statistics and subjected the qualitative data to content analysis. The results revealed that overall the teachers' differentiation was at a moderate or low rate. The most common dimensions for differentiation were assessment, teaching methods, and support materials. Learning environment and teaching arrangements were the least employed differentiation dimensions. The most significant challenges for differentiation were large class sizes and lack of time and resources. The results of this study give preliminary indications that differentiation should be implemented more in Dutch secondary EFL teaching and addressed in more depth already in pre-service teacher education. Moreover, based on this study, Dutch EFL teachers would need more resources to differentiate their teaching in a more profound manner. The results of this study have implications for EFL teaching also in other contexts.