In this work, a newly competitive electrochemical sensor for oxazepam detection was successfully achieved. Ag-Pt core-shell nanoparticles supported on graphene nanosheets were used for the sensor construction (Ag-Pt/GRs/GCE) for the determination of oxazepam in real samples including serum, urine and tablets. The properties of materials were characterized by transmission electron microscopy, scanning electron microscope, electrochemical impedance spectroscopy and voltammetry. The voltammetric obtained data confirm the significant enhancement of reduction current and reduction overvoltage oxazepam at a surface of Ag-Pt/GRs/GCE. After optimization of electrochemical parameters employing this modified electrode at pH 7.0, the reduction peak currents for oxazepam was found linearly with concentrations in the range of 0.05-150.0 mu M with detection limit of 42 +/- 1 nM using differential pulse voltammetry method. The simple fabrication method, specificity, high sensitivity, good reproducibility and long-term stability as well as acceptable accuracy for oxazepam detection in real samples are the main advantages of this sensor, which might have broad applications in drug diagnostics.