To characterize biofilm formation of a chlorobenzoates (CBs) degrading bacterium, Burkholderia sp. NK8, with another bacterial species, and the biodegradation activity against CBs in the mixed-species biofilm. Burkholderia sp. NK8 was solely or co-cultured with each of five other representative bacteria in microtitre dishes. Biofilm formation involving the strain NK8 was synergistically promoted by co-culturing with only Pseudomonas aeruginosa PAO1. Epifluorescent microscopy revealed that cells of the bacterial strain NK8 were viable and distributed randomly in the mixed-species biofilms. Enumeration of the attached cells on the surface of wells revealed that cells of the strain NK8 increased approx. 10-fold by the co-culture with the strain PAO1 compared to those by monoculture of the strain NK8, and the degradation activity of 3-chlorobenzoate by the dual-species biofilms was more promoted than that by the strain NK8-monocultured biofilms. Enhanced biofilm formation of Burkholderia sp. NK8 by the bacterial consortium occurred, but is determined by the partner bacterial species. The mixed-species biofilms have the advantage to degrade CBs on a solid surface. This study provides a significance of bacterial consortia on the biofilm formation and the degradation activity of Burkholderia sp. NK8, which contribute for complete degradation of chlorinated aromatics.