This study examines the adoption of English as a Medium of Instruction (EMI) in higher education institutions in Mongolia, Japan, and South Korea, focusing on the influencing factors of global university rankings and international collaborations. Through thematic analysis of semi-structured interviews with 45 implementers from six case-study private higher education institutions, the findings indicate that the global university rankings influenced the case-study universities' decision to adopt the EMI policy. Program implementers emphasized national and global university ranking systems as key external influences. Additionally, international collaboration, such as joint/dual degree programs and exchange programs with foreign partner universities, significantly impacted the adoption of EMI.