This study introduces a new electrochemical platform for the rapid and sensitive detection of the potent anticancer drug epirubicin (EPB) in blood plasma. The platform utilizes a graphene/Zinc Oxide (ZnO) nanoparticle nanocomposite modified glassy carbon electrode (GCE), which was synthesized through a simple one-pot method where ZnO nanoparticles were dispersed onto graphene sheets. The graphene/ZnO/GCE nanocomposite was characterized using advanced techniques such as FE-SEM, EDS, XRD, FT-IR, and XPS in order to analyze its structural properties. The graphene/ZnO/GCE electrode exhibited minimal interference and demonstrated high selectivity and sensitivity in detecting EPB. The sensor's selectivity was validated by a recovery rate exceeding 98.40 % and a relative standard deviation below 4.65 %. The limits of detection and quantification were determined to be 6.0 nM and 9.0 nM, respectively, indicating the sensor's high sensitivity within a practical concentration range. With a sensitivity of 1.09509 µA/µM, the sensor exhibited a linear response to EPB concentrations ranging from 4.0 to 730.0 μM. Furthermore, successful detection of EPB in serum samples with a recovery rate exceeding 98.40 % underscores the practical utility of the graphene/ZnO/GCE sensor. The detailed characterization of the graphene/ZnO/GCE nanocomposite provides insights into its structural and chemical attributes, furthering its potential for biomedical applications.