The taxonomic status of an actinobacterial strain isolated from Mariana Trench sediment was determined using a polyphasic taxonomic approach. The strain, isolate MT1.1(T), formed a distinct clade in the Micrococcineae 16S rRNA gene tree together with Dermacoccus nishinomiyaensis DSM 20448(T). The organism had chemical and phenotypic properties consistent with its classification in the genus Dermacoccus and could be distinguished from D. nishinomiyaensis DSM 20448(T) using DNA-DNA relatedness and phenotypic data. The G + C content of the DNA of isolate MT1.1(T) was 65.2 mol%. It is evident that the organism merits recognition as a novel species in the genus Dermacoccus. The name proposed for this taxon is Dermacoccus abyssi sp. nov.; the type strain is MT1.1(T) (=DSM 17573(T) = NCIMB 14084(T)). The organism grows well at 40 MPa and hence is piezotolerant.