Photocatalysis is an important method for degradation of dyes and organic pollutants in waste water. In this studynovel trimetal nanoparticles La/Bi/Cu were synthesized by a simple chemical reduction method using sodium borohydride as a reducing agent. The synthesized trimetal nanoparticles were characterized by XRD, SEM, EDAX, FTIR and UV-VIS spectra to study the crystalline size, morphology, elemental composition and surface properties of nanoparticles. The size of the nanoparticles was determined by using XRD and found to be in the range of 10.86nm-61.46nm. The photocatalytic activity of synthesized La/Bi/Cutrimetal nanoparticles was assessed by photocatalytic decomposition of Methylene Blue dye under solar light irradiation. [ABSTRACT FROM AUTHOR]