In the present study, the biosorption of Astrazon Blue FGRL (AB) which is one of the cationic dyes most commonly used in nylon and acrylic textiles from aqueous solution was studied onto tea waste (tea dust discharged after using), a waste lignocellulosic material. The effects of different parameters including biosorbent dosage, initial pH, contact time, initial dye concentration, and temperature were studied. Tea waste was characterized by Brunauer-Emmett-Teller (BET) surface area, FTIR, and SEM. The experimental equilibrium data were fitted to the Langmuir and Freundlich isotherms. The Freundlich isotherm model fitted to the experimental data better than the Langmuir isotherm. The maximum biosorption capacity, q(max), was found to be 263.16 mg/g. The experimental data were discussed in detail comparing with some other low-cost adsorbents reported for AB removal in the previous literature, considering q(max), adsorbent surface area, experimental conditions, isotherm models, and thermodynamics of the AB adsorption. The thermodynamic data indicated that AB biosorption was feasible but nonspontaneous, endothermic, and a chemisorption reaction.