The principle aim of this study was to decolorize Reactive Blue 19 dye with Bacillus megaterium(B. megaterium) and to determine the effect of some parameters such as pH, temperature, initial dye concentration, nitrogen and carbon sources
 on decolorization. With this purpose, a new isolate identified as B. megaterium by genotypic (16S rRNA sequence) characterization, was found effective on Reactive Blue 19 decolorization. Glucose (20g/L) was found as the most suitable carbon
 source for Reactive Blue 19 decolorization with a yield of 92%. When the effect of nitrogen sources on decolorization was
 investigated, the highest dye removal rate was found as 91% which was obtained in shake flask containing yeast extract (10
 g/L). In trials determining pH effect on dye removal; it was found that B. megaterium enables decolorization of Reactive Blue
 19 at neutral pHs with a high percentage of 91%. P values were calculated for all parameters and found as p<0.05. Results of
 FTIR analysis showed that decolorization of Reactive Blue 19 by B. megaterium occurred via biodegradation. When chemical
 and physical wastewater treatment methods were compared to the biological methods, usage of microbial sources such as
 B. megaterium is considered as an efficient and economical alternative.