In this work, an alternative to deactivate noxious green tide Tetraselmis suecica in the short-term is proposed by employing Perovskite-like cube-shaped, crystalline CaTiO3 semiconductors functionalized with atomic silver nanoparticles. CaTiO3 was prepared by a microwave-assisted hydrothermal method and then Ag(0)NPs (1 wt% of CaTiO3), were added by the photoreduction method. The XRD results show that crystalline CaTiO3 has an orthorhombic unit cell with a Perovskite-like structure. Images obtained by FESEM and HRTEM microscopies show well-faceted CaTiO3 rectangular prismatic morphology functionalizated with silver nanoparticles similar to 13.5 nm. XPS and EDS-FESEM has confirmed the composition of CaTiO3 and silver occurring mainly as reduced metal. The UV inactivation of noxious T. suecica with Ag/CaTiO3 nanocomposites formed on bare materials results in complete deactivation of the algae in 12 min. The direct contact between harmful algae and Ag/CaTiO3 nanocomposite is necessary to deactivate the algae and inhibits algae viability. (C) 2013 Elsevier BM. All rights reserved.