OBJECTIVE: To evaluate if state death investigation systems affect the reporting of suicides, particularly when comparing medical examiners to coroners. DATA SOURCES AND STUDY SETTING: We used restricted-access state mortality data from National Vital Statistics System between the years 1959 to 2016. These data were matched with state-level changes in death investigation systems reported by the Centers for Disease Control and Prevention database on the Public Health Law Program: Coroner/ME Laws. STUDY DESIGN: We used difference-in-differences and event study methods for the analysis. We estimated the relative per capita changes in suicides, accidental deaths, and homicides when comparing coroner-only states with other death investigation types. Sub-analyses estimated differences by sex, race, and if coroners were required to receive training. DATA COLLECTION/EXTRACTION METHODS: Not Applicable. PRINCIPAL FINDINGS: Coroners-only states underreported suicides by 17.4% (p < 0.05) and performed 20.4% (p < 0.05) fewer autopsies compared to states with county coroners and a state medical examiner. This pattern is consistent by sex and race. Required coroner training did not affect death determination significantly. CONCLUSION: Coroners-only states underreported suicides compared to states with county coroners and a state medical examiner. The disparity in the use of autopsies is a potential mechanism for underreporting of suicides by coroners. If all coroners-only states adopted a state medical examiner, suicide reporting would increase by 2243-3100 deaths in the United States annually.