The enterprise of sustainability science extends beyond the academy to address pressing environmental issues through collaboration. It coincides with trends in higher education institutions (HEIs) towards an expanded mission for addressing societal challenges as well as greater accountability. In this paper, we aim to establish an instrument for assessing the performance of sustainability science initiatives in HEIs. The performance of three HEI--community partnerships for sustainability science in Ontario, Canada (the Brock-Lincoln Living Lab, the Excellence in Environmental Stewardship Initiative, and Niagara Adapts) were examined using the HEI--Community Partnership Performance Index (HCPPI). Our preliminary results suggest that the HCPPI is a reliable, valid, and easy-to-administer tool for accurately assessing the performance of HEI--community partnerships for sustainability science. Incorporating systemic performance assessments into HEI--community partnerships promotes accountability, transparency, and continuous improvement. It also serves as a vital feedback mechanism by fostering refection, adaptation, and learning--critical components to sustainability science.