The aim of this work is to evaluate decolorization of Basic Blue 41(BB41) by non acclimatized Pseudomonas aeruginosa, which was isolated from a non-dye contaminated activated sludge biomass. The effect of initial BB41 concentration, temperature, pH, inoculum size and growth medium (different nitrogen and carbon sources) on decolorization were investigated. P. aeruginosa was able to use BB41 as a sole carbon source and decolorize 25 mg/L BB41 with the efficiency of 99.4% without any additional carbon or nitrogen source. Initial BB41 concentration, temperature, pH, inoculum size and different nitrogen and carbon sources have a considerable effect on decolorization of BB41. 250 mg/L yeast extract was found sufficient for completely removal of 200 mg/L BB41 at 35 degrees C within 72 hours.