<![CDATA[This study investigates the implementation of Differentiated Instruction (DI) in English vocabulary learning and its contribution to student engagement among senior high school EFL students in Indonesia. The study addresses learner diversity in readiness, interests, learning preferences, and prior vocabulary knowledge. A quantitative quasi-experimental design was employed at SMAN 7 Soppeng, South Sulawesi, involving 11th-grade students assigned to an experimental group receiving DI and a control group receiving conventional instruction. Vocabulary mastery was measured using pre-tests and post-tests, while student engagement was assessed through a questionnaire adapted from the National Survey of Student Engagement and examined across behavioral, emotional, and cognitive dimensions. The experimental treatment incorporated varied content, activities, grouping, and experiences, including visual, auditory, and kinesthetic activities, to accommodate students’ different learning needs. Data were analyzed using descriptive statistics and an independent-samples t-test for vocabulary outcomes, while engagement responses were analyzed descriptively. The findings indicate that DI produced positive changes in students’ engagement. Behavioral engagement increased through more active participation, attentiveness, and classroom contributions. Emotional engagement improved through greater interest, confidence, and motivation, accompanied by lower reported anxiety. Cognitive engagement showed the most notable development, reflected in the use of vocabulary grouping, journaling, peer teaching, games, storytelling, and deeper processing strategies. Overall, the findings suggest that DI provides a responsive and inclusive approach to vocabulary instruction by creating varied learning pathways that support active participation, positive learning experiences, and meaningful cognitive engagement among Indonesian senior high school EFL students.]]>
