The electrochemical characteristics of vitamin K-3 (denoted VK3) incorporated in acid-treated multiwalled carbon nanotubes (MWNTs)-chitosan (CHIT) hybrid films in phosphate buffer solutions were determined and the electrocatalytic oxidation of dopamine (DA) was investigated. It was shown that the adsorbility of VK3 on the surface of a glassy carbon electrode was greatly enhanced by CHIT and MWNTs. Cyclic voltammetric measurements revealed that the redox peak currents of VK3 increased dramatically with the addition of MWNTs. The apparent charge-transfer rate constant k(s) and transfer coefficient alpha for electron transfer between the electrode surface and immobilized VK3 in MWNTs-CHIT hybrid films and in MWNT films were calculated as 21.4 s(-1), 0.49 and 3.2 s(-1), 0.47, respectively. The electrocatalytic oxidation of DA evaluated by cyclic voltammetric measurements indicates that VK3-MWNTs-CHIT hybrid film modified electrodes have good electrocatalytic property to DA. The differential pulse voltammograms were used to detect the DA concentration. A linear relationship between steady-state current and DA concentration was obtained over the range of 2-100 mu mol/L with a detection limit of 0.18 mu mol/L. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3130089] All rights reserved.