In this work, the decolorization of crystal violet dye in aqueous solution by corncob-based and phosphoric acid-activated carbon was addressed. Equilibrium data were successfully applied to study the kinetics and mechanism of adsorption of dye onto both carbons. Adsorption increases with pH increase from 2 to 5, but a further increase in pH has no effect on adsorption. Quantitative removal of dye at a higher initial pH of the dye solution reveals the basic nature of the crystal violet and the acidic nature of the activated carbons. Langmuir equation gave good fitting for adsorption results, with a high removal capacity of 320.0mg/g. Kinetic results indicate that adsorption process followed a pseudo-second-order equation (R2=0.998) and intra-particle diffusion is the most probable operating mechanism. This suggests that corncob-based and phosphoric acid-activated carbon is an efficient crystal violet adsorbent and that it possess good potential for crystal violet removal in wastewater treatment.