Several mesoporous silicas (MCM-41, SBA-15, MCF-17, and MCF) with a different texture, pore size, and surface area were synthesized by a hydrothermal method. These parent materials were then functionalized with 3-mercapto propyl trimethoxy silane (MPTMS), and this was followed by oxidation of thiol groups to the corresponding sulfonic group. Prepared materials were characterized by infrared spectroscopy, X-ray diffraction, thermal and elemental analysis, and then used as carries to study loading and release of tamoxifen citrate as an anti-cancer drug by UV–Vis spectroscopy. The optimization measurements of time and amount of drug loading indicated a higher loading of tamoxifen citrate in SBA-15-SO3H and MCM-41-SO3H. The release of tamoxifen as a function of time and pH in the presence and absence of NaCl was investigated. Results showed a fast kinetic of drug release in MCF-SO3H in an acidic condition in the presence of NaCl.