Western Hemisphere species of bombardier beetles in the carabid tribe Ozaenini are distributed from southern Arizona and southern Texas to southern Chile, with more than 80% of described species being endemic to the tropics. Recent taxonomic works variously classify the 145 described species into six or 17 genera, indicating general disagreement on what constitutes natural lineages in the group. This study provides the first phylogenetic analysis of the Western Hemisphere Ozaenini using DNA sequence data from the mitochondrial and nuclear genomes. In the resulting trees, the following three suprageneric clades are supported by high bootstrap and posterior probability values: the Ozaena group (Ozaena Olivier Platycerozaena Bänninger Goniotropis Gray), the Tropopsis group (Tropopsis Solier Entomoantyx Ball and McCleve), and the Pachyteles group (Pachyteles Perty Physea Brullé Tachypeles Deuve Inflatozaena Deuve Filicerozaena Deuve Proozaena Deuve Serratozaena Deuve). Close relationship among genera within the Ozaena group, and among genera within the Pachyteles group were not predicted and have not previously been hypothesized. Among the most surprising results is that Pachyteles (sensu lato) and Goniotropis are not sister groups, but rather represent well-defined and distantly related clades. The phylogeny inferred from molecular sequence data led to discovery of morphological characters unique to the Pachyteles group that clearly distinguish members of Pachyteles (sensu lato) from Goniotropis. These morphological characters are described and illustrated. Results provide evidence for polyphyly of the genera Pachyteles, Tachypeles and Goniotropis as they are currently defined. Adults of Tachypeles moretianus Deuve and Serratozaena Deuve are reported for the first time to be myrmecophilous.