Objectives. To examine temporal trends in the classification of opioid-involved overdose deaths (OODs) and racial variation in the classification of specific types of opioids used. Methods. We analyzed OODs coded as other or unspecified narcotics from 1999 to 2018 in the United States using data from the National Vital Statistics System and the Centers for Disease Control and Prevention. Results. The total proportion of OODs from unspecified narcotics decreased from 32.4% in 1999 to 1.9% in 2018. The proportion of OODs from unspecified narcotics among African American persons was approximately 2-fold greater than that of non-Hispanic White persons until 2012. Similarly, the proportion of OODs from unspecified narcotics among Hispanic persons was greater than that of White persons until 2015. After we controlled for death investigation system, African American persons had a higher incidence rate of OODs from unspecified narcotics compared with White persons. Conclusions. There have been significant improvements in the specification OODs over the past 20 years, and there has been significant racial disparity in the classification of OODs until about 2015. The findings suggest a health data disparity; the excessive misclassification of OODs is likely attributable to the race/ethnicity of the decedent.