Abstract Based on Hyland’s (2018) interpersonal model of metadiscourse, this study explores MOOC video lecturers’ use of metadiscourse and compares it to traditional university lecturers’. Disciplinary variation in metadiscourse in the MOOC video lectures has also been investigated. The MOOC corpus consists of sixteen MOOCs across three disciplinary areas, including Arts and Humanities, Engineering and Physical Sciences, and Social Sciences. The results suggest that despite slight differences, the most frequently appearing metadiscourse in the MOOC corpus resembles the patterns found in university lectures, which reveals the remarkable similarities in using metadiscourse between MOOCs and traditional face-to-face lectures. However, different instructional contexts and teacher-student relationships indeed contribute to the variance in the employment of metadiscourse. Overall, MOOC video lecturers employed more interactive metadiscourse but less interactional metadiscourse than university lecturers. Cross-disciplinarily, the use of metadiscourse in MOOC video lectures is considerably influenced by disciplinary features. MOOCs containing more discipline-specific content and requiring intensive cognitive effort tend to use more interactive metadiscourse and engagement markers; while for MOOCs that may include more perspectives than basic facts, boosters and attitude markers seem to be employed more frequently. Possible reasons and purposes of the differentiated use of metadiscourse across disciplines are discussed in detail.