This systematic review article analysed and evaluated the current literature on sustainable educational technology in higher-education institutions (HEI). University stakeholders aspire to have any educational technologies employed be sustainable beyond short-term solutions. Identifying these sustainable factors requires reviews of recent studies, particularly with the insightful experience of the recent pandemic. Unfortunately, systematic reviews on sustainability were few and focused more on specific modalities. Hence, this present study reviewed past studies (published between 2015 and 2021) to identify the types of educational technology or modality being studied on the aspects of sustainability, the topic of interests that contribute to the challenges in online learning, and the themes and subthemes that are critical to the sustainable use of online education. Guided by the preferred reporting items for systematic reviews and meta-analyses (PRISMA) to review five journal databases (Scopus, ProQuest, Web of Science (WoS), Emerald and Google Scholar), 44 articles were analysed systematically. Four themes emerged from the analysis: technology related, teaching and learning, ethical aspects, and instructional support, as well as 12 subthemes. A conceptual framework was proposed, and other recommendations were discussed at the end of the paper for future research.