Ag/CuPO4 nanocomposite was successfully synthesized using wet chemistry for potential application as a mechanism to suppress charge recombination and harvest more photons in thin-film organic solar cells (TFOSCs). The morphological and optical properties of the nanocomposite were studied using high-resolution electron microscopy and UV–vis spectroscopy. The Ag/CuPO4 nanocomposite exhibited a semispherical geometry which is suitable for the occurrence of localized surface plasmon resonance (LSPR) and light scattering in a dielectric medium. Conventional device architecture is employed that uses a solar absorber composed of a poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend with and without the nanocomposite. As a result, significant changes in the device performances were observed by the incorporation of the metal nanocomposite, where the experimental evidence suggested that the doped active layer outperformed the undoped ones. Consequently, the best power conversion efficiency (PCE) grew by nearly 95% compared to the reference cell. Furthermore, the measured photocurrents are found to be dependent on the concentration of the nanocomposite in the absorber layer. In this article, the effects of metal nanocomposite are discussed in terms of the phenomena of local surface plasmon resonance and far-field scattering in the photoactive medium of TFOSCs.