English Medium Instruction (EMI) in university courses is expected to have positive effects on university students' English language learning in non-English-speaking countries since they can learn English on campus (Macaro, 2018). For successful second language learning, efficient use of second language (L2) learning strategies is essential (Cohen & Wang, 2018; Oxford, 2017).The goal of this dissertation is to investigate, through a mixed method research design, how the experiences of EMI impact Korean university students' learning strategies for effective English learning. The data for this research were collected through class observations of eighty-eight students in two EMI classes and in-depth interviews with two instructors and two focus groups of five students at a Korean national university from April 2019 to June 2019. One of the classes was for first-year students who were taking an EMI course for the first time and the other for second or third-year students who had taken more than two EMI classes before. My data analysis yielded the following findings: (1) students who had taken more EMI classes used more learning strategies than the others, (2) students used social strategies more often than the other strategies to understand complicated subject matters such as syntax, and (3) students combined different strategies to increase their understanding. The study concludes that students perceive EMI courses as effective and helpful for their English language learning and that more experiences with EMI can increase their use of learning strategies, which would facilitate their English learning. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]