Dye pollutants from research laboratories are one of the major sources for environmental contamination. In the present study, a nutraceutical industrial fennel seed spent (NIFSS) was explored as potential adsorbent for removal of ethidium bromide (EtBr) from aqueous solution. The adsorbent was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Through batch experiments, the operating variables like initial dye concentration, adsorbent dosage, temperature, contact time, and pH were optimized. Equilibrium data were analyzed using three number of two-parameter and six number of three-parameter isotherm models. The adsorption kinetics was studied using pseudo-first order and pseudo-second order. The diffusion effects were studied by film diffusion, Webber-Morris, and Dumwald-Wagner diffusion models. The thermodynamic parameters; change in enthalpy (ΔHº), entropy (ΔSº), and Gibbs free energy (ΔGº) of adsorption system were also determined and evaluated.