The novel Enterobacter strains TS1L and TS3, isolated from textile wastewater, showed a good ability to decolourise Basic Red 9 (BR9). The effects of various physicochemical parameters on decolourisation efficiency were evaluated using both single and mixed culture of Enterobacter sp. The optimal conditions for the decolourising activity of strains TS1L, TS3 and a mixed culture were as follows: textile wastewater as sole substrate without glucose addition, pH 7.0, 150 rpm, 35 degrees C and 12 h of incubation. The highest decolourisation rate was observed at 81.15% for the single culture of strain TS1L. Moreover, TS1L not only reduced BR9 in wastewater, but also improved the quality of the water under optimal conditions. The treated wastewater met the criteria of the Water Quality Standard (Thailand). Based on gas chromatography-mass spectrometry, TS1L completely degraded BR9 and converted it into organic compounds. To our knowledge, this is the first report of Enterobacter with the ability to decolourise BR9 dye.