Education for Sustainable Development (ESD) is a crucial approach to foster transformative change in education at higher education institutions (HEIs). The implementation of ESD in Malaysia has not yet been mainstream. Prior to the extensive implementation of ESD at HEIs, it is imperative to guarantee that university teachers possess the requisite qualifications in competencies for effective instruction. This chapter presents a study that was conducted to assess the level of ESD-related competencies among university teachers. In particular, the competencies in this study were framed by the concept of key sustainability competencies (KSCs) and pedagogical content knowledge (PCK). The study additionally compares the competencies of university teachers according to their research fields, natural sciences or social sciences. The study employed a quantitative survey method, gathering data from 267 university teachers representing 20 Malaysian public universities. Descriptive statistics were used to summarise the overall competency levels, while inferential statistical tests, such as independent t-tests, were conducted to compare the competencies between teachers from different research fields. The findings revealed that Malaysian university teachers demonstrated moderate competency levels overall. A statistically significant difference was observed, with social science teachers exhibiting higher competency levels in both KSCs and PCK compared to those in natural sciences. These results underscore the importance of interdisciplinary approaches and highlight the evolving understanding of sustainable development as encompassing both natural and social science perspectives. The study concludes with recommendations for targeted professional development programs, strategic institutional planning, and policy reforms to mainstream ESD effectively in Malaysian HEIs.