A trimetallic, MoO3·CuO·ZnO nanocomposite was synthesized by co-precipitation method. The nanocomposite was characterized by X-ray diffraction (XRD), scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDS), atomic forcce microscopy (AFM) and photoluminescence (PL). Particle size was determined to be 40.34 nm by using Scherrer’s formula from XRD data. The SEM–EDS mapping shows that all the elements in this composite are not confined in a single site, rather they are distributed in a solid matrix. PL study of the MoO3·CuO·ZnO nanocomposite showed spectral variation through size and morphology with calcination temperature. Photocatalytic activity of the composite was studied under visible light irradiation. The composite showed excellent visible light dye degradation efficiency of 95.82% at pH 9.