Large-scale uniform ternary ZnIn₂S₄ nanosheet array films have been grown on indium-tin oxide (ITO) glass substrates effectively by a simple direct elemental reaction route. Inorganic–organic bulk heterojunction photovoltaic devices were fabricated with ZnIn₂S₄ film as an electron acceptor and poly (2-methoxy-5-(2/-ethylhexoxy)-1,4-phenylene vinylene (MEH-PPV) polymer as electron donor. The formation of the ZnIn₂S₄ nanosheet film was characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and UV-VIS-NIR spectroscopy. The as-prepared ZnIn₂S₄ nanosheet film was demonstrated as an n-type semiconductor exhibiting an apparent photocurrent response and good photostability. The photovoltaic performance of the constructed solar cell device with the active structure of ITO/ZnIn₂S₄:MEH-PPV/Au was evaluated at room temperature under AM1.5G (100 mW cm⁻²) simulated globe sun illumination from a filtered Xenon lamp.