Background Despite the fact that the A6 mortality reporting system has been operating for almost 20 years in Vietnam, there has been no systematic evaluation of the system. This study assesses the completeness, sensitivity and positive predictive value of the system in relation to injury related mortality. Methods Evaluation of the A6 system was undertaken in three (geographically distributed) provinces in Vietnam. Deaths identified in the A6 system were compared with deaths identified by an independent consensus panel to determine the per cent completeness of the A6 system. Verbal autopsies (VA) were conducted for all identified deaths from the consensus panels, and the sensitivity and positive predictive value of the A6 system were assessed using the VAs as the reference. Results 5273 deaths were identified from the A6 system with a further 340 cases identified by the independent consensus panel (total n1=45613). Injury related deaths accounted for 13.6% (n1=4763) of all deaths with an overall injury mortality rate of 55.3 per 100 000 person years. The per cent completeness of the A6 system in relation to injury deaths was 93.9% with a sensitivity of 75.4%, specificity of 98.4% and positive predictive value of 88.4%. Conclusions The A6 mortality reporting system is embedded within the commune health system and is the lead mortality reporting system for the Ministry of Health. The system performs well in relation to its completeness and classification of injury related deaths. With further enhancements and ongoing support from government and donor agencies, the A6 system will be a valuable resource for identifying and planning preventive strategies targeting the leading causes of injury related deaths in Vietnam.