Cyclic voltammetry (CV) was performed on tamoxifen (tam) using different electrodes and in various acidic electrolytes containing 10% v v(-1) methanol (MeOH). Tam oxidation was found to be most favorable using 0.1 mol L-1 H2SO4. To investigate the mechanism, we performed chronoamperometry, CV at different scan rates, differential pulse anodic voltammetry (DPAV), and electrochemical impedance spectroscopy on tam-covered glassy carbon electrodes (GCEs). The electrode area, diffusion coefficient, and surface concentration (Gamma) of tam were calculated to be 0.062 cm(2), 3.65 x 10(-6) cm(2) s(-1), and 3.2 x 10(-10) mol cm(-2) respectively. Then the effects of different parameters on the DPAV were optimized. The best conditions were 2.5% v v(-1) cMeOH, 0.1 mol L-1 H2SO4, deposition potential 0.4 V, deposition time 30 s, and GCE rotating rate 400 rpm. Therefore, the calibration curve was plotted in the range of 0.5 to 5 mu g mL(-1). The limits of detection and quantitation (LOD and LOQ) were found to be 0.008 and 0.025 mu g mL(-1), respectively. The relative bias and standard deviation of 2 mu g mL(-1) tam were estimated to be 5% (n = 5) and 2.3%, respectively. Finally, the proposed method was successfully employed for the determination of tam in real samples.