In the present work, we prepared quaternary chalcogenide (Cu2NiSnS4) nanoparticles and electrochemically exfoliated graphene (EEG) nanosheets to use as a nanohybrid counter electrode for Dye-sensitized solar cells (DSSC). The structural analysis revealed that the crystallite size of Cu2NiSnS4 in its nanohybrid is smaller than the pristine Cu2NiSnS4 nanoparticles. Further, it is observed from the morphological studies that the Cu2NiSnS4 nanoparticles are decorated uniformly over the wrinkled graphene nanosheets. The electrochemical behavior of these materials is analyzed by AC impedance spectroscopy, cyclic voltammetry (CV) and Tafel polarization studies demonstrating the positive synergetic effect of graphene and Cu2NiSnS4 in Cu2NiSnS4/Graphene nanohybrid. Due to the exceptional electron-transfer pathway of graphene and the excellent catalytic ability of Cu2NiSnS4 nanoparticles, the prepared nanohybrid exhibits excellent electrocatalytic activity towards tri-iodide reduction than the pristine Cu2NiSnS4 nanoparticles and graphene nanosheets. The DSSC fabricated using Cu2NiSnS4/graphene nanohybrid counter electrode shows a higher photoconversion efficiency (PCE) of 7.92% than that fabricated using std. Pt (7.68%) and the prepared pristine Cu2NiSnS4 CE (7.20%).