This paper investigates the differences in college learners' perceptions and correlations of factors related to willingness to communicate (WTC) in an English mediated instruction (EMI) class. Based on a survey of 50 collegiates (33 males, 17 females) and two rounds of interviews with 15 students, the t-tests showed that there were not many statistical differences depending on learner characteristics except the learners' grade difference affecting their perception of improvement in English. However, depending on the course types, the Kruskal-Wallis test showed statistically significant differences in the categories of present level of participation, expected level of participation with L1 option, question & answer, group collaboration, active listening, and preference to EMI with L1 option. Furthermore, the factors of WTC appeared strongly correlated with their perceptions on the improvement in English, increased confidence, and the extent of learning in the EMI class. According to qualitative analyses of open-ended questions in the survey and interviews, the learners thought group presentations in English were most difficult. They also responded that their low English proficiency, peer pressure, and the student-orientedness in class made them passive and less confident. The learners, however, adopted diverse coping strategies to overcome such difficulties. They were also positive about the limited use of L1 in the EMI class. Implications for EMI are suggested.