A single walled carbon nanotube-chitosan (SWCNT-chitosan) modified disposable pencil graphite electrode (PGE) was used in this study for the electrochemical detection of Vitamin B(12). Electrochemical behaviors of SWCNT-chitosan PGE and chitosan modified PGE were compared by using cyclic voltammetry (CV), square-wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) techniques. SWCNT-chitosan modified electrode was also used for the quantification of Vitamin B(12) in pharmaceutical products. The results show that this electrode system is suitable for sensitive Vitamin B(12) analysis giving good recovery results. The surface morphologies of the SWCNT-chitosan PGE, chitosan modified PGE and unmodified PGE were characterized by using scanning electron microscopy (SEM).