A cellulolytic bacterium, strain P2-1(T), isolated from soil in Thailand, was characterized using a taxonomic approach based on phenotypic and chemotaxonomic characteristics and the 16S rRNA gene sequence. The novel strain was Gram-positive, facultatively anaerobic, spore-forming and rod-shaped. It contained meso-diaminopimelic as the diagnostic diamino acid in the cell-wall peptidoglycan. The DNA G+C content was 52.7 mol%. The major isoprenoid quinone was MK-7. Anteiso-C(15 : 0) and iso-C(16 : 0) were the dominant cellular fatty acids. Phylogenetic analyses using the 16S rRNA gene sequence showed that the novel strain was affiliated to the genus Paenibacillus. Strain P2-1(T) was closely related to Paenibacillus cineris KCTC 3998(T), P. favisporus KCTC 3910(T) and P. rhizosphaerae KCTC 13015(T) with 96.3-96.5 % gene sequence similarity. DNA-DNA relatedness, physiological characteristics and some biochemical characteristics clearly distinguished strain P2-1(T) from related species of the genus Paenibacillus. Therefore, strain P2-1(T) represents a novel species of the genus Paenibacillus, for which the name Paenibacillus cellulositrophicus sp. nov. is proposed. The type strain is P2-1(T) (=KCTC 13135(T)=PCU 305(T)=TISTR 1888(T)).