The ability of soil microorganisms to decolorize Reactive Red 141, an industrial textile dye used commonly in Southeast Asia, including Thailand, was analyzed. Incubation experiments showed that the dye was decolorized under a static anoxic condition of liquid medium inoculated with soil microorganisms, while it was not decolorized in a shaking aerobic condition. Fourteen isolated bacteria that decolorize the dye were identified and found to belong to Gram-positive bacteria, such as Bacillus, and Gram-negative bacteria, such as Stenotrophomonas. Attenuated total reflectance fourier transform infrared (ATR-FTIR) analysis suggested that the intermediate products of degradation of the dye were naphthalene derivatives and other smaller compounds produced by oxidative cleavage of the dye, irrespective of the difference of the strains. Together with the variety of the phylogenetic locations of the isolated strains, this suggested that the reaction is catalyzed by non-specific enzyme(s) under an anoxic condition.