Assessing the integration of sustainability in higher education can be a powerful lever for organisational change in higher education institutions. When comparing the available tools and instruments for assessment of sustainability in higher education, the Auditing Instrument for Sustainability in Higher Education (AISHE) has proven to be a reliable tool, providing a qualitative approach to sustainability assessment. This article presents the AISHE tool and discusses its use in two higher education institutions in Belgium. Included in this work is an analysis of the audits in several study programs, and an independent evaluation of the instrument based on literature and Belgian good practices. The experiences of the Belgian institutions with sustainability assessment tools can motivate other higher education institutions around the world to start up sustainability assessment in their institution.