The growing phenomenon of university courses designated as English-medium-instruction (EMI) worldwide presents new demands for non-native-English-speaking educators. However, adequate preparation and professional learning support for them to teach academic subjects in English remain a challenge. An understanding of their challenges and professional learning (PL) needs in EMI teaching is critically needed. This review examines 115 articles in English and Chinese on PL for EMI educators in HE, covering numerous countries. It critically reviews the literature to identify the common challenges in EMI teaching, and "how" and "to what extent" educators are prepared and supported for EMI teaching. Findings revealed EMI educators are often found unprepared and/or inadequately supported for their new roles. They face multiple challenges when embarking on EMI teaching. The review reveals misalignments between challenges facing educators and formal PL on offer. It also highlights the importance of informal ongoing PL and educators' agency in orchestrating their learning.