This chapter explores the complexities and challenges involved in English as a Medium of Instruction (EMI) and the professional development of EMI educators. It highlights the need for comprehensive training programs that go beyond language proficiency, incorporating pedagogical strategies, cultural awareness, and subject-specific challenges. The chapter emphasizes that while EMI teachers often face difficulties due to insufficient training in teaching methodologies, there is also a lack of structured and pedagogically supported EMI training programs globally. It reviews various studies and professional development practices across different countries, pointing out the need for continuous, interdisciplinary, and context-sensitive professional development that fosters collaboration and enhances educators’ confidence and creativity. The need for more in-depth, evidence-based research on the effectiveness of these training programs is also stressed, with a focus on how local educational policies, socio-economic conditions, and institutional characteristics influence EMI practices. The chapter concludes with recommendations for improving the quality and effectiveness of EMI teaching through more structured and comprehensive training programs.