Many higher education institutions (HEIs) have started to incorporate sustainable development (SD) into their system. A variety of sustainability assessment tools (SATs) have been developed to support HEIs to systematically measure, audit, benchmark, and communicate SD efforts. In recent years, stakeholders have increasingly asked HEIs to demonstrate their impacts on SD. These impacts are the direct and indirect effects an HEI has outside of its organizational boundaries on society, the natural environment, and the economy. This study analyzes to what extent SATs are capable of measuring the impacts that HEIs have on SD. A mixed-method approach, using descriptive statistics and an inductive content analysis, was used to examine 1134 indicators for sustainability assessment derived from 19 SATs explicitly designed for application by HEIs. The findings reveal that SATs largely neglect the impacts HEIs have outside their organizational boundaries. SATs primarily use proxy indicators based on internally available data to assess impacts and thus tend to focus on themes concerning the natural environment and the contribution to the local economy. Updating existing SATs and developing new ones may enable HEIs to fully realize their potential to contribute to SD.