This research aimed to find out the perspectives that secondary school English teachers in Kabupaten Solok have on Differentiated Instruction, the implementation, and the challenges faced in the classroom. This research was qualitative in the form of a case study. Data collection was based on questionnaires, in-depth interviews, document analysis, and part1c1pant observation. Informants who became data sources in this study were selected based on purposive sampling, namely teachers who teach in grade X (Fase E), have got the individual training about the 'Kurikulum Merdeka', and have more than IO years of English teaching experience. Based on these criteria and the willingness of the teachers, 8 English teachers in grade X (Fase E) of SMA in Kabupaten Solok were selected as informants in this study. The next step was to conduct in-depth interviews to explore the informants' understanding and perspectives on Differentiated Instruction. Then, the teaching module documents were analyzed and classroom observations were made on how to implement the plan in the teaching module. The data obtained was that informants showed their understanding of Differentiated Instruction obtained from the process of self­learning and peer discussions. However, in terms of planning on the teaching modules prepared, not all informants have clear planning on Differentiated Instruction. Similarly, it was found during classroom observations that not all informants implemented Differentiated Instruction by the required aspects and considerations, namely paying attention to students' learning readiness, interests and talents, and learning styles. In summary, it could be concluded that the informants have explained their understanding of Differentiated Instruction in theory. However, this was not the case when it came to planning the teaching module and implementing it in the classroom. There were still informants who showed confusion and incomprehension in terms of the application of Differentiated Instruction in lesson planning and implementation in the classroom.