Mesoporous silica SBA-15 synthesized by hydrothermal method has been used as template silica and sucrose as the carbon source, in preparation of CMK-3. This was carboxylated by ammonium persulfate ((NH 4 ) 2 S 2 O 8 ) and H 2 SO 4 , and functionalized with L-Cysteine methyl ester hydrochloride. The resulting samples were characterized by Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), and Nitrogen adsorption–desorption measurements (BET). The functionalized product shows the BET surface area of 548.4m 2 g −1 and pore diameter 26.1Å. Cadmium sorption conditions such as the pH value, contact time, adsorbent dose, in batch system have been optimized. Under the experimental conditions, the adsorption capacity for cadmium has been 198mgg −1 . The increment in the Cd(II) adsorption capacity of CMK-3 functionalized with L-Cysteine is attributed to the oxygenous and thiols functional groups formed on the surface of CMK-3 which can react with Cd(II).