Purpose: This study aims to show how a massive open online course (MOOC) can be used as an educational tool to diffuse specialised corporate sustainability research globally to a broad range of learners. Design/methodology/approach: This study is based on insights from the design and implementation of a sustainable fashion MOOC. The MOOC was launched in late 2019 on a global learning platform and has recently passed 40,000 enrolments (February 2022). The presentation of the MOOC draws on quantitative and qualitative data available to instructors on the global learning platform. Findings: Based on the data about the learners and their use of the MOOC, this study demonstrates how MOOC can be a powerful tool to diffuse sustainability research to new groups of learners, who differ significantly from the typical students at business schools and universities in the West. Moreover, the findings also demonstrate how the COVID-19 pandemic had a significant impact on the MOOC's popularity. Originality/value: This study provides new empirical evidence on how sustainability research can be translated into online education material of relevance for a broad range of learners from around the world. Moreover, the study also points to the number of practical and structural challenges linked to the future mainstreaming of MOOCs and other types of online education material.