Herein, a new copper/mercury‐based amalgam electrode with 45 wt % copper was introduced. An amalgam electrode with the lowest mercury content among all amalgam electrodes, reported so far,was introduced. The method of making and activating the electrode was investigated and the working conditions were established. The as‐prepared electrode was employed to determine azathioprine(Aza) using differential pulse adsorptive stripping voltammetry (DPASV) method. The required factors were considered for the electrode voltammetric response to evaluate and optimize Aza level. The proper response of this electrode was obtained in Brinton‐Robinson buffer(BRB) (pH 2) at −0.15 V for 200 seconds. The electrode response to the target compound was linear in the concentration range from 0.04 to 1.0 μM. The detection limit was found to be about 1.6×10−8 M. The relative standard deviation (RSD) for 5 determinations was obtained to be about 3.5 % (the average of RSDs calculated for all concentrations, represented in the calibration curve). The method was successfully applied for Aza determination in plasma and urine samples which led to satisfactory results. It can be concluded that the presence of high levels of potential interfering agents such as ascorbic acid and cysteine did not affect the Aza determination.