This study explored the prioritization of English-medium instruction (EMI) teachers' needs for faculty development and institutional support by applying a best-worst scaling approach to an EMI program in Japan. This prioritization is important as EMI programs need management under various constraints (e.g., time, budget, and teachers). This study also investigated how teachers' needs for institutional support differ by English language competence and EMI teaching experience and their relationship with EMI programs (e.g., full-time or adjunct). Questionnaire surveys administered to 38 EMI teachers revealed that, overall, faculty development (FD) program menus training teaching styles, speaking skills, communication skills, and respecting the diversity of students should be prioritized such that it varies depending on the teachers' English language competence levels but not their teaching experience. Irrespective of their relationship with EMI programs, the recognition and appreciation of their burdens, efforts, and contributions is most needed. There are noticeable differences based on their position over the necessity of pedagogical guidelines, teaching load, and economic incentive.