Synthetic dyes are being employed by industries, especially by textile industries. About 10 to 15 percent of synthetic dyes are wasted during dying process and enter industrial wastewaters as toxic and harmful pollutants. These kind of dyes are not only a threat to water resources, soil and atmosphere, but also cause serious problems for living organisms particularly humans in the ecosystem. Therefore, removing them from environment is imperative. Various physical and chemical methods for textile dyes degradation from wastewaters have been developed but they are extremely costly. In recent years, biodegradation approach because of its cost-effectiveness and safety has been used as an alternative and safe method. In this method, microorganisms, particularly bacteria are used for removing dyes. In this study, however, we used Acinetobacter lwoffii bacteria. Decolorization by these bacteria was investigated by a system which contained both medium and dye. Furthermore, decolorization optimizing parameters of Indigo carmine including time, initial dye concentration, pH and temperature were investigated. The results demonstrated that over a period of 54 h, at 50 ° C, 150 mg/l of concentration and pH=9, maximum decolorization of 99.02 percent was performed.