In this study, the biosorption of two commonly used dyes, namely Acid Blue 225 (AB 225) and Acid Blue 062 (AB 062), from aqueous solutions by Bacillus amyloliquefaciens biomass was studied in a batch system with respect to initial dye concentration, pH, adsorbent dosage, and contact time. The biomass exhibited maximum uptake at pH 1 due to its positive nature at acidic pH and the anionic nature of the dyes. Kinetic studies showed that the biosorption of dyes on biomass was a gradual process. An equilibrium was reached in 90 min for both dyes. The kinetic studies indicated that a pseudo-second-order rate equation was able to provide a realistic description of biosorption kinetics of the dyes. The constants obtained from the pseudo-second-order kinetic model at different temperatures were evaluated and the activation energies for the biosorption of AB 225 and AB 062 were found to be 13.52 and 13.62 kJ/mol, respectively. Isotherm studies pointed out that biosorption of dyes on biomass followed the Langmuir isotherm model. The adsorption capacity of biomass for AB 225 and AB 062 were 111.15 and 112.19 mg/g, respectively. Thermodynamic quantities that characterize the biosorption phenomena, i.e. enthalpy, entropy, and free energy change of the adsorption, were calculated leading to a conclusion on the efficiency of the properties of the biosorbent-dye systems.