Health system performance assessment (HSPA) is a promising tool to evaluate health system capacity in achieving health systems goals and informed policy for health systems strengthening. Despite its importance, no universal definition is available at global level to support HSPA implementation. This chapter highlights the evolution of HSPA frameworks, which mostly follow the scope and boundaries of health systems. Key characteristics of successful HSPA include regularity, transparency, comprehensiveness, being analytical and systematic, which result in valid assessment and inform policy. HSPA requires selection of indicators suitable to the country context; the criteria for selecting indicators include importance, relevance, feasibility, reliability and validity. Hospital performance assessment, a subset of the HSPA, is necessary as it consumes signification portion of health resources. HPSA also contributes to monitoring achievement of SDG targets 3.8.1 and 3.8.2 on Universal Health Coverage as committed by countries. The chapter concludes by providing evidence how Thailand's health system performed in response to COVID-19 pandemic.