The integration of critical thinking in vocational English education is increasingly urgent for 21st-century workforce preparation. However, vocational schools in developing countries like Indonesia struggle to move beyond rote memorization toward reflective learning. This study investigates how deep learning is enacted to develop critical thinking in English classrooms and identifies implementation challenges in Indonesian vocational education. Using a qualitative design, in-depth interviews were conducted with five English teachers at vocational high schools in Tana Toraja, Indonesia. Data were analyzed using Miles and Huberman’s interactive model. Findings reveal that teachers enact deep learning through contextualized materials aligned with students’ vocational fields, higher-order questioning, collaborative activities (project-based learning and discussions), facilitative teaching roles, and supportive classroom climates. These practices foster students’ ability to analyze problems, question information, defend arguments, and transfer critical thinking beyond the classroom. However, implementation faces significant challenges: teacher-level factors (time limitations, conceptual gaps, administrative burden); student-related challenges (mixed abilities, low confidence, unpreparedness for independent learning); institutional barriers (limited technology, assessment complexities); and cultural factors where respect for authority hinders questioning. The study implies that sustainable critical thinking development requires multi-level interventions: context-specific professional development, reduced administrative workload, improved infrastructure, curriculum reforms prioritizing depth over breadth, and culturally responsive pedagogies.