Locally available bentonite clay has been modified by magnesium and used to eliminate acid blue 129 from aqueous solutions. The adsorption was studied under different experimental conditions such as dye concentrations, temperature, and shaking time. The adsorption of the dye increased with time and followed the pseudo-first-order kinetic with rate constant “k” 0.126 min^-1 at 283 K. Thermodynamic parameters such as ΔH°, ΔS°, and ΔG° were calculated from the slope and intercept of the linear plots of ln K against 1/T. Analysis of adsorption results obtained at temperatures of 283, 293, 303, and 313 K showed that the adsorption pattern on bentonite seems to follow Langmuir and Freundlih. The increase in temperature reduces adsorption capacity by magnesium-modified bentonite due to the enhancement of the desorption step in the mechanism. The activation energy of the adsorption process was found to be 3.55 kJ mol^-1. The Mg-bentonite showed better adsorption than Ba and Al-bentonite. Our study reveals that abundantly available local clay may be used to eliminate dyes from aqueous solutions.