In the present investigation, the adsorption performance of sesame (Sesamum indicum) oil cake, a waste biomass from the oil extraction industry for remediation of Basic Blue 26 (BB 26) from aqueous media was examined. Effects of pH, adsorbent dosage, BB 26 concentration, shaking time temperature, and ionic strength on BB 26 adsorption have been studied in detail. The residual cake was characterized based on FTIR, zeta potential, SEM-EDAX, and BET techniques. Isotherm and kinetic data have been well-exemplified by Freundlich and pseudo second-order equations, respectively. Maximum uptake capacity was reported to increase significantly from 54.52 mg/g for unmodified cake powder to 91.24 mg/g for ZnCl2-modified cake powder, establishing the importance of ZnCl2 activation. The mechanism of BB 26 adsorption on cake powder was reported to involve different steps as predicted from the fitting of kinetic data to Weber-Morris equation. Thermodynamic studies showed that the process of BB 26 adsorption onto cake powder was accompanied by an increase in entropy and reported to be endothermic and spontaneous. Significant recovery and uptake capacity values were reported from the first to the last cycle of reusability. Due to ease of recovery and regenerability, ZnCl2-modified cake powder has been established as a promising remedy for the successful elimination of BB 26 from aqueous media.