In the mirror universe, the Denobulans were a subject species of the Terran Empire.

It is unknown when they submitted to the empire; however, it occurred some time prior to 2155 as there were Denobulans already serving on board Imperial Starfleet vessels by that time.

Although many Terrans had a distrust or bias towards the alien races they had subjugated, Denobulans had seemed to have garnered a limited amount of respect. In fact, it was probably their willingness to submit to the empire's will that had won them that respect; Commander Jonathan Archer was heard to remark that it was not in the Denobulans' nature to rebel against the empire (ENT episode: "In a Mirror, Darkly").