An aerobic actinomycete, designated SCSIO 01299(T), was isolated from a deep-sea sediment collected from the northern South China Sea at a depth of 3258 m. The isolate was found to be a natural producer of the synthesized antitumour agent deoxynyboquinone and its three new derivatives, pseudonocardians A, B and C. A blast search based on almost-complete 16S rRNA gene sequences showed that strain SCSIO 01299(T) had high sequence similarities with members of the genus Pseudonocardia. The 16S rRNA gene sequence phylogenetic tree revealed that strain SCSIO 01299(T) was a member of the genus Pseudonocardia. Phenotypic analysis, chemotaxonomy and DNA-DNA relatedness could readily distinguish the isolate from established members in this genus. It was concluded that strain SCSIO 01299(T) represents a novel species, for which the name Pseudonocardia antitumoralis sp. nov. is proposed. The type strain is SCSIO 01299(T) ( = DSM 45322(T) = CCTCC M 2011255(T)).