Vitamin K-3 (VK3), a synthetic blood coagulation vitamin with fat-solubility, easily results in side-effect in animal body due to its toxicity and improper addition of animal feedstuffs. In this study, a novel sensor based on glassy carbon electrode (GCE) modified with a conducting polymer-both nano-noble metals and two-dimensional nano-carbon composite consisting of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), carboxymethyl cellulose (CMC) and reduced graphene oxide@palladium (rGO@Pd) was successfully used for the voltammetric detection of VK3 in animal blood and feedstuff samples. Under the optimized conditions, PEDOT:PSS-CMC-rGO@Pd/GCE/GCE displayed the excellent synergistically electrocatalytic ability for the electrochemical oxidation-reduction of VK3, which exhibited a good voltammetric response for VK3 in the concentration range from 4 x 10(-7) to 9 x 10(-5) M, with a limit of detection of 1.4 x 10(-8) M. Furthermore, a facile preparation, high sensitivity, good selectivity, superior sensing stability, and satisfactory practicability of PEDOT:PSS-CMCrGO@Pd/GCE/GCE for sensing VK3 suggested that the potential applicability of PEDOT:PSS-CMC-rGO@Pd provided a promising electrochemical sensing platform for the determination of VK3 in pharmaceutical and feed inspection. (C) 2016 Elsevier B.V. All rights reserved.