ZnO/graphene nanocomposites and carbon-doped ZnO were synthesized via a modified citrate route, providing a facile, cost-effective, and environmentally benign pathway for tailoring the optoelectronic properties of ZnO-based materials. X-ray diffraction analysis confirmed the formation of a highly crystalline hexagonal wurtzite ZnO structure. The emergence of a distinct diffraction peak near 25° in the ZCO-II sample indicated the incorporation of graphene-related carbon phases, confirming successful nanocomposite formation. Optical characterization revealed a pronounced red shift of the absorption edge from approximately 400 nm for pristine ZnO to nearly 800 nm for carbon-modified samples, extending the photoresponse from the ultraviolet region into the visible and near-infrared ranges. Carbon incorporation also resulted in a reduction of crystallite size to ~30 nm and a marked narrowing of the optical band gap, decreasing from 3.18 eV (pure ZnO) to 2.35 eV in the composite system. These structural and optical modifications highlight the effectiveness of the citrate route in engineering ZnO-based nanomaterials with enhanced light-harvesting capability. The prepared materials demonstrate strong potential for applications in photocatalysis, chemical sensing, and optoelectronic device technologies.