Graphene-based nanocomposites are emerging as a new class of materials that hold promise for many applications. In this study, we demonstrate a simple one-pot hydrothermal method for the synthesis of PrPO₄–reduced graphene oxide (RGO) nanocomposites using graphite oxide, praseodymium(III) nitrate and disodium hydrogen phosphate as starting materials. The as-prepared samples were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and UV-vis diffuse reflectance spectroscopy. It was revealed that the RGO sheets were decorated with the in situ-formed PrPO₄ nanorods to form a well-combined composite structure. The PrPO₄–RGO nanocomposites show enhanced photocatalytic activity in comparison with bare PrPO₄ nanorods in the degradation of methylene blue (MB) under simulated sunlight irradiation, which may be attributed to the improved separation of electron–hole pairs and the increased ˙OH amount in the reaction system. The facile method could be extended to design other graphene-based photocatalysts for energy and environmental applications.