In this study, the adsorption mechanism of three reactive azo dyes (Everzol Black B, Everzol Red 3BS, Everzol Yellow 3RS H/C) on natural porous minerals, sepiolite and zeolite, have been examined in order to identify the ability of clay minerals on the removal of colored textile dyes from aqueous solutions. High ion exchange capacity, high surface areas and importantly their relatively cheap prices make them attractive adsorbents. For this purpose, series of batch adsorption tests were carried out as a function of solids concentration, time and dye concentration using natural and modified sepiolites and zeolites. Also, experiments were conducted to determine the amount of solid to be used in adsorption tests. An optimum solids concentration was selected as 0.05g/mL (5%). Most of the adsorption was found to take place within the first 2 h of mixing, taking into account the extreme changes like pH and concentration, the mixing period was selected as 4h for further testing. The adsorption results indicate that both natural sepiolite and zeolite have limited adsorption capacities of the reactive dyes but are substantially improved by modifying their surfaces with quaternary amines. The mechanism of adsorption process is elucidated on the basis of experimental data.