While English as the medium of instruction (EMI) is becoming a popular institutional practice across the globe, the bulk of research has yielded inconsistent findings regarding its effectiveness for students' content and language learning. Through a qualitative inquiry into students' EMI experiences in a Macau university, the study discovered that content learning and language proficiency are vague terms to describe students' learning outcomes, which consist of multiple dimensions, including knowledge mastery, access to information, disciplinary professionalism, academic/disciplinary English and Chinese proficiency, etc. While EMI promoted student learning in some dimensions, it failed in others, and it is unrealistic to judge the overall effectiveness of EMI as a curriculum provision. The study confirms previous research findings on EMI as an ineffective means for knowledge mastery and further exposes this as a problem that can hardly be remedied by raising admission requirements on students' English proficiency in English as a foreign language (EFL) contexts. Additional issues and challenges of EMI were identified in the study, including a quandary in promoting students' bilingual academic and disciplinary proficiency in English and their mother tongue. Suggestions for future research are given, and ideas for possible measures to help students cope with EMI in EFL contexts are discussed.