The purpose of this study was to investigate ESL learners’ attitudes toward the use of English as a medium of instruction at Mindanao State University, Marawi, Lanao del Sur, Philippines. Furthermore, it tried to examine the challenges they encountered in the use of English as a medium of instruction. This study is guided by two different frameworks: the ABC Model of Attitudes of Eagly & Chaiken (1998) and the Problems of English as a Medium of Instruction (EMI) by Tanveer (2007). Thirty (30) undergraduate students from the College of Education majoring in English took part in the study by completing a survey questionnaire based on Ghani’s (2015), using convenience sampling. This study further utilized a descriptive qualitative research design to explore their perceptions. The data from the Likert scale questionnaire were tabulated and computed, specifically the mean and standard deviation, as well as direct content analysis for the open-ended question. The major findings of this study were as follows: (1) the majority of participants had positive affective, behavioral, and cognitive attitudes toward English as a medium of instruction; (2) some of the challenges encountered were self-related cognition challenges, linguistic challenges, and challenges associated with the role of language instructor. Finally, this provided significant implications and recommendations for educators and curriculum planners by revealing the challenges encountered by students when using EMI, thereby suggesting that they must carefully plan and design curriculum in alignment with the students' needs and interests so as to enhance learning using the target language.
 Keywords: English as a medium of instruction (EMI); Attitudes; Learning Anxiety