Background: In Thailand, hospital accreditation (HA) is widely recognized as one of the system tools to promote effective operation of universal health coverage. This nationwide study aims to examine the relationship between accredited statuses of the provincial hospitals and their mortality outcomes. Method: A 5-year retrospective analysis of the Universal Coverage Scheme's claim dataset was conducted, using 1 297 869 inpatient discharges from 76 provincial hospital networks under the Ministry of Public Health. Mortality outcomes of 3 major acute care conditions, including acute myocardial infarction, acute stroke, and sepsis, were selected. Results: Using generalized estimating equations to adjust for area-based control variables, hospital networks with HA-accredited provincial hospitals showed significant associations with lower standardized mortality ratios of acute stroke and sepsis. Conclusion: Our findings added supportive evidence that HA, as an organizational and health system management tool, could help promote hospital quality and safety in a developing country, leading to better outcomes.