The healthcare sector's direct and indirect GHG emissions account for 4%–5% of global net emissions. Hospitals face the challenge of sustainable transformations and need to measure, monitor, and report on their sustainability performance. While indicator-based assessments of hospital sustainability have received increased attention over the last years, they are heterogenous in their terminologies, categories, and included indicators. This study reviews taxonomies and included indicators in hospital sustainability assessments, laying the foundation for future developments of consistent indicator-based assessments. The objective is to (1) critically review existing assessments of hospitals; (2) identify relevant sustainability topics in a hospital context and derive a best-practice categorization; (3) highlight thematical gaps. Based on the PRISMA method, we identify 88 relevant articles. First, 47 articles (comprehensive hospital sustainability assessments with extensive indicator sets) are reviewed, forming the basis for deriving a best-practice categorization. Second, considering an additional 41 articles (proposing indicators for specific hospital aspects), we collect all indicators and compile a consolidated indicator pool. We find substantial variations in the taxonomies and terminologies of the reviewed articles; most notably, there is a disagreement about what constitutes an indicator. 73% of all consolidated indicators are qualitative, and 78% are site-specific. Thematical gaps relate to sustainability along upstream and downstream value chains (esp. food and pharmaceuticals) and quantitative social indicators in general. The developed best-practice taxonomy and the compiled indicator pool serve as a comprehensive basis for future sustainability assessments of hospitals.