Two aerobic, Gram-stain positive actinobacterial strains with nematicidal activity, designated HA11164(T) and HA12591, were isolated from mangrove sediments in Hainan, China. Phylogenetic analysis based on the 16S rRNA gene sequences indicated that strains HA11164(T) and HA12591 belong to the genus Pseudonocardia and are closely related to Pseudonocardia carboxydivorans (with the similarities of 98.30 and 98.24 %, respectively), Pseudonocardia alni (98.23 and 98.16 %, respectively) and Pseudonocardia antimicrobica (98.10 and 98.03 %, respectively). The major polar lipids of the strain HA11164(T), as a representative strain of the two strains, were found to consist of phosphatidylmethylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine, phosphatidylinositol, five unidentified glycolipids and four unidentified polar lipids. The predominant menaquinone of strain HA11164(T) was identified as MK-8 (H4), and the major fatty acids were identified as iso-C16:0, C17:1 ω10, C16:0 and C16:1 ω9. The G+C content of strain HA11164(T) was determined to be 74.9 mol%. The DNA-DNA relatedness values between strains HA11164(T) and P. alni, Pseudonocardia tropica, Pseudonocardia antarctica, P. carboxydivorans and Pseudonocardia parietis were 58.3, 56.2, 50.0, 57.1 and 46.0 %, respectively. Based on the results of this polyphasic study, strains HA11164(T) and HA12591 are considered to represent a novel species of the genus Pseudonocardia, for which the name Pseudonocardia nematodicida sp. nov. is proposed. The type strain is HA11164(T) (=CGMCC 4.7118(T) = DSM 45940(T)).