Thiol-functionalized mesoporous silicas have been synthesized by co-condensation of tetraethoxysilane and varying contents of 3-mercaptopropyltrimethoxysilane in acidic medium with the block copolymer Pluronic 123 as a structure directing agent. Adsorption of lead in aqueous solution on the synthesized materials has been investigated. The adsorption data are fitted to Langmuir isotherms and a maximum adsorption capacity calculated from the Langmuir equation can reach 0.19 mmol of Pb/g. The stoichiometric ratio of S: Pb being 1:1 has been obtained for every adsorbent. The effect of the pH on lead adsorption, and desorption of lead on the lead-loaded materials have been studied.