Siderophores are low molecular weight organic ligands excreted by aerobic soil microorganisms and some plants roots to acquire Fe. Siderophores may also complex other metals such as Cd, therefore, may influence bioavailability, toxicity and mobility of Cd in soils. The main objective of this study was to investigate the effects of desferal siderophore (DFOB) on adsorption of Cd on montmorillonite. The adsorption of Cd on montmorillonite was studied as a function of pH (Cd concentration: 1mg L-1) in the range of 3-7.6, and as a function of metal concentration (Cd concentration in the range of 0.1-1 mgL-1) in the absence and presence of siderophore (DFOB concentration 250 mM) using a 24 h batch equilibration experiments. The results of adsorption envelopes (pH dependent experiments) showed that the siderophore deceased sorption of Cd onto montmorillonite at pH³5. The results of equilibrium test (isotherms) revealed that removal of Cd from solution was affected by siderophore at both pHs. Siderophore decreased adsorption of Cd by the mineral. The Freundlich and Langmuir isotherms were described satisfactorily equilibrium data. The values of Freundlich (KF) and Langmuir (KL) bonding constants were greater in suspensions without siderophore as compared to suspensions containing siderophore. These values are indication of competition between siderophore and the clay surfaces for Cd ions.