Thiourea formaldehyde alginate resin (TUFA) was prepared and characterized performed by Fourier transform infrared spectrometer (FT-IR) spectra, scanning electron microscope (SEM)/EDS, Energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD). The amphoteric grafting resin used for removal of both anionic Congo red (CR) and cationic crystal violet (CV) dyes individual from aqueous solutions by batch adsorption method. The adsorption–desorption behaviors of TUFA resin were investigated under various pH values, initial CR and CV concentrations, contact time, solution temperatures, adsorbent dose and ionic strength were examined by batch technique. The highest sorption capacities of CR and CV after 90 min at 25 C were found at pH of 5 and 9, respectively. The equilibrium data were analyzed by the isothermal adsorption models and the applicability of empirical kinetic models was also studied. The maximum monolayer coverage (qe) from Langmuir isotherm model was determined to be 559.55 and 237.77 mg. g–1 for CR and CV respectively. The kinetic adsorption behavior gives the best agreement to pseudo-second order model of the experimental data. Thermodynamic parameters including ΔG, ΔS and ΔHwere determined over the temperature range of 293–318 K. The results revealed that adsorption reaction of both dyes was spontaneous endothermic and physical in nature.