Given the fact that English is the global academic lingua franca, the implementation of English-mediated instruction (EMI) has inevitably gained momentum in higher-education institutes (HEI) in Taiwan. However, before the full-scale implementation of EMI education, it is imperative to gain an insightful understanding of Taiwanese EFL learners' perspectives on EMI courses. An online survey of 467 Taiwanese EFL learners who had never taken EMI courses before was conducted. Two independent variables of psychological properties (basic psychological needs, BPNs; psychological capital, PsyCap), one dependent variable (willingness to take EMI courses, WtT), and a moderator (perceived value of English, PVE) form the proposed research model. The results show that all five hypotheses were supported; specifically, EFL learners' BPNs influence on their WtT was significant but negative. A positive indirect effect was discovered with the mediation of PsyCap, which significantly and positively affected WtT. PVE was a significant moderator in the relationship of both BPNs and PsyCap with WtT; however, the moderating effect was negative in the former and positive in the latter. The novelty of this study is that it is the very first research to explore EFL learners' willingness to take EMI courses from the perspectives of two important psychological properties.