A novel endophytic actinomycete, strain GMKU 931(T), was isolated from the root of a wattle tree, Acacia auriculiformis A. Cunn. ex Benth., collected at Kasetsart University, Bangkok, Thailand. Strain GMKU 931(T) produced short spiral chains of smooth-surfaced spores on the aerial mycelium. Lysine and meso-diaminopimelic acid were present in the cell-wall peptidoglycan. Whole-cell hydrolysates contained galactose, madurose and mannose. The predominant menaquinones were MK-9(H(6)) and MK-9(H(8)). The major fatty acids were iso-C(16 : 0) and iso-C(16 : 1). The major phospholipids were phosphatidylinositol and phosphatidylglycerol. A phylogenetic analysis based on 16S rRNA gene sequences suggested that strain GMKU 931(T) forms a distinct phyletic line within the recently proposed genus Actinoallomurus. The significant differences in phenotypic and genotypic data indicate that strain GMKU 931(T) represents a novel species of the genus Actinoallomurus, for which the name Actinoallomurus acaciae sp. nov. is proposed. The type strain is GMKU 931(T) (=BCC 28622(T) =NBRC 104354(T) =NRRL B-24610(T)).