Korea Advanced Institute of Science and Technology (KAIST), an elite science and engineering school, has implemented English-medium instruction (EMI) since the mid-2000s and provided a systematic multilevel curriculum of English for academic purposes (EAP) since 2014. In order to further customize English language education according to the needs of individual majors and departments, integrated content and language (ICL) courses were introduced for the first time in 2018. Two undergraduate ICL courses, one in biology and the other in mechanical engineering, were offered in the spring of 2018. This study investigates how the two courses were carried out and what the outcome of the courses was and attempts to make suggestions for the future implementation of undergraduate ICL courses. Interviews with the content professors, EFL (English as a Foreign Language) professors, and teaching assistants were conducted, and students’ course evaluations and course materials, including the syllabi and handouts, were analyzed. Results show that the two courses were introduced through different routes - one from the top-down approach and the other from the bottom-up approach. Both were successful in terms of students’ satisfaction levels, but the content professors showed widely different attitudes to their ICL courses, and their satisfaction levels differed. The EFL professors also had different opinions on their collaboration with the content professors. The study concludes with suggestions on how to improve the offering of ICL courses in the future.