As a contribution to the ongoing studies on English as a medium of instruction (EMI) policy in non-native English-speaking countries, we explored the implementation of EMI in public upper secondary schools in the region of Rabat-Salé-Kénitra in Morocco as a case study. In particular, we examined EMI public upper secondary school teachers' perceived benefits of teaching maths and science through English. Semi-structured interviews were conducted with six EMI public upper secondary school maths and science teachers, who were the total number of the teachers recruited by the Moroccan Ministry of National Education in the whole region in the 2021-2022 academic year. The findings revealed that four teachers considered their EMI teaching experience to be beneficial. Using EMI improved their English language proficiency, made access to teaching resources easier, encouraged them to read more content in English and collaborate with English language teachers, enabled them to develop a bilingual teaching expertise in both English and French and diversify their language abilities. However, two EMI teachers considered using EMI as a burden. They cited difficulties with the additional lesson planning required. Additionally, lack of prior EMI teaching experience and training also made their EMI experience difficult. Suggestions for improvements included additional training and providing more compensation for teaching EMI courses, to account for the extra work and time required.