Cefotaxime sodium has an antibacterial effect and it is classified as a third-generation broad spectrum cephalosporin antibiotic. It is irreversible, oxidized at the glassy carbon electrode in various buffer systems and at different pH values. The detailed mechanism of the oxidation process is described in this manuscript. Differential pulse and square wave voltammetric methods were developed for its determination in pharmaceutical dosage forms and spiked human serum samples according to the linear relation between the peak current and cefotaxime sodium concentration. For analytical purposes, a very well resolved diffusion controlled voltammetric peak was obtained in Britton-Robinson buffer at pH 2.0 at 0.87 and 0.89V for differential pulse and square wave voltammetric techniques, respectively. The linear response was obtained within the range of 1x10(-6) - 6x10(-5) M with a detection limit of 2.83x10(-7) M for differential pulse and 2x10(-6) - 6x10(-5) M with a detection limit of 3.61x10(-7) M for square wave voltammetric techniques. The repeatability and reproducibility of the methods for both media (supporting electrolyte and serum sample) were determined. Precision and accuracy of the developed method were used for the recovery studies. The standard addition method was used for the recovery studies. No electroactive interferences were found in biological fluids from the endogenous substances and additives present in pharmaceutical dosage form.