The purpose of this study was to investigate the removal of Fast Green FCF dye from aqueous solutions using Flower Gel in a batch adsorption process. The effect of different parameters such as pH, contact time, adsorbent dosage, stirrer speed and temperature were studied, and various isotherms including Langmuir, Freundlich and Tempkin were applied. The adsorbent characteristics were determined by microscopic analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction and ultraviolet-visible (UV-vis) spectrophotometry. The results showed that the equilibrium experimental data fitted well to the Langmuir isotherm and the maximum adsorption capacity for this adsorbent was 58.82 mg/g. The adsorption kinetic data followed the pseudo-second-order kinetic model and the thermodynamic parameters of the adsorption, such as Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°), showed that the Fast Green FCF adsorption process by Flower Gel was spontaneous and exothermic in nature.