Abstarct: Antibiotics are being used in veterinary and human medicine widely, yet these compounds, when released into the environment, have potential risks for aquatic and terrestrial organisms. In order to achieve a high removal rate of azithromycin from aqueous solution, a novel modified nano-diatomite was prepared first by a physical treatment that is grinding raw diatomite to the scale of nano and then applying chemical treatment by impregnating nano-diatomite into a saponin solution. Adsorbent characterization was performed using X-ray Diffraction (XRF), Brunauer-Emmet-Teller (BET), scanning electron microscopy (SEM), Dynamic light scattering (DLS) and Energy Dispersive X-ray Spectrometry (EDX). Different adsorption conditions such as adsorbent dosage, pH, initial concentration and contact time were investigated. It was shown that the maximum removal percentage of azithromycin from aqueous solution with the initial concentration of 20ppm of azithromycin for raw nano diatomite and saponin-modified nano diatomite were 95.5% and 99%, respectively. Fourier transform infrared (FTIR) results revealed that azithromycin was adsorbed by O-H and C=C on the diatomite surface. Weber-Morris intra-particle diffusion model results suggested that while IPD is not the rate-controlling step for high concentrations, it is the only step that controls the rate of adsorption in low concentrations of azithromycin. Generally, although both adsorbents had shown an excellent performance in removal of azithromycin from solution, modification of nano-diatomite had led to a higher efficiency in the adsorption process.