A bacterial strain, designated CKOBP-6T, isolated from a contaminated laboratory plate, was characterized by using a polyphasic taxonomic approach. Chemotaxonomic and morphological properties of the strain were consistent with its classification in the genus Paenibacillus. Cells were Gram-variable, aerobic, sporulating, motile rods. 16S rRNA gene sequence analysis demonstrated that this novel isolate was unique, showing 94.6 % sequence similarity to Paenibacillus chitinolyticus NBRC 15660T and lower levels of similarity to Paenibacillus gansuensis KCTC 3950T (93.8 %) and Paenibacillus terrigena A35T (93.8 %). The novel isolate could be distinguished from the type strains of all of these species based on a range of phenotypic data. The major cellular phospholipids were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and one unknown phosphoglycolipid. The predominant isoprenologue was an unsaturated menaquinone with seven isoprene units (MK-7). The major fatty acids of strain CKOBP-6T were C(16 : 0) (12.0 %), anteiso-C(15 : 0) (52.0 %) and iso-C(16 : 0) (16.4 %). The G+C content of the genomic DNA was 51.2 mol%. It is evident from the genotypic and phenotypic data that strain CKOBP-6T should be classified as a representative of a novel species of the genus Paenibacillus, for which the name Paenibacillus contaminans sp. nov. is proposed. The type strain is CKOBP-6T (=BCRC 17728T=LMG 24216T).