Purpose: Universities strategically organize themselves around sustainability, including transformative goals in teaching and learning. Simultaneously, the role of online education has become more prominent. This study aims to better understand the purpose and process of creating online sustainability education (OSE) and to identify challenges and opportunities for implementing these courses and programs to achieve universities' broader transformative sustainability goals. Design/methodology/approach: This study uses a multiple case study design to research three universities in diverse geographical and institutional contexts (Finland, the USA and Colombia). Qualitative data was collected by interviewing program-related experts (n = 31) and reviews of universities' strategic documents. Findings: The findings suggest that despite important advances, further attention is merited regarding aligning the purpose of OSE with student learning outcomes, clarifying the values underlying the process of online program/course creation and developing transformative and process-oriented approaches and pedagogies to implement OSE. The authors also highlight emerging challenges and opportunities in online environments for sustainability education in different institutional contexts, including reaping the benefits of multilocality and diverse student experiences regarding sustainability issues. Originality/value: There is a paucity of studies on university-level sustainability education in relation to online environments. This research expands on the existing literature by exploring three different geographical and institutional contexts and shedding light on the relationship between the practical implementation of OSE and universities' broader sustainability goals.