Regulatory agencies are increasing the pharmacogenomic information in their official drug labeling. However, despite the importance of regulatory harmonization, this implementation may not be running in parallel among major agencies. Comparing labeling of medicines approved by different agencies may identify gaps to solve. Our study compared the cytochrome P450 pharmacogenetic information included in the United States (US) Food and Drug Administration (FDA) drug labels and European Union (EU) Summaries of Product Characteristics (SmPCs). US labels presented significantly more specific pharmacogenetic subheadings (51 vs 26%), more prevalence and pharmacokinetic data for each metabolic phenotype (59 vs 25% and 82 vs 48%, respectively) and more applicable information about dose modifications required (25 vs 5%). Approximately 75% of the US labels evaluated scored higher on the overall quality than the analogous EU SmPCs, and this difference was not associated with the time since the EU SmPCs' last review. To enhance harmonization, regulatory agencies should simultaneously introduce the pharmacogenetic information in their drug labeling.