Lecturers teaching on English-medium instruction (EMI) programs are expected to deliver complex disciplinary content through English, a language which they themselves may not be fully proficient in. This can compromise student comprehension and learning unless lecturers are equipped with the necessary tools to effectively transmit knowledge in a second language. To provide EMI lecturers with training relevant to their specific needs, empirical evidence from EMI settings is crucial. However, little is known about what actually transpires in the EMI classroom, particularly concerning lecturer-student interaction and lecturers’ use of communication strategies (CSs). This study fills the gap by investigating how experienced and highly rated EMI lecturers in a Chinese university overseas campus use explicitness strategies to increase the clarity of instruction and facilitate student comprehension in interactive academic activities. The data, comprising 10 h of tutorials and 10 h of supervisor-student supervision meetings, is analyzed from an English as a lingua franca (ELF) perspective based on an adapted Conversation Analysis (CA) approach. In total, 12 types of explicitness strategies are identified, among which self-repetition, self-repair and self-paraphrase are the most frequently used. Different strategies are used depending on the specific situation, such as the use of self-repetition and self-repair when introducing new knowledge or concepts, the use of self-paraphrase when explaining a difficult technical term, and the use of self-expansion when giving instructions. The findings of this study have implications for the training of lecturers who face challenges in delivering disciplinary content in English and communicating effectively with multilingual students in the EMI setting.