Abstract: The aim of this research is to study the adsorption of mercury from aqueous media by an Acetobacter xylinum biofilm. Effects of pH, adsorption time, initial concentration and the adsorbent dosages on the adsorption of mercury were studied. The influence of pH on the adsorption onto the biofilm was studied in the pH range. The surface charge density varied with pH and the concentration of mercury adsorbed significantly increased from pH 5.0 to maximum levels at pH 8.0. Adsorption equilibrium was established after about 50 min, after which point the level of adsorbed mercury did not significantly change with time. The adsorption equilibrium was also represented with Langmuir and Freundlich adsorption isotherms. The adsorption capacity was 180 mg g-1. Desorption studies were performed with hydrochloric acid. The results suggest that an Acetobacter xylinum biofilm could be used as an effective adsorbent for the removal of mercury.