In the present work, a simple and new electrochemical biosensor was designed based on a magnetic bar carbon paste electrode (MBCPE) modified with iron oxide and silver nanoparticles (Fe3O4@Ag) for DNA detection. MBCPE/Fe3O4@Ag composite was used for the self-assembly monolayer (SAM) of thiolated single stranded DNA (SH-DNA). The morphology of Fe(3)O(4)NPs and Fe(3)O(4)NPs@Ag was studied by scanning electron microscopy (SEM), infrared spectroscopy (IR) and UV/Vis methods. Also, electrochemical techniques were applied for characterization of the designed biosensor. The experimental conditions (the immobilization and hybridization processes) were optimized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. MBCPE/Fe3O4@Ag/ssDNA biosensor revealed a wide liner range and low detection limit (0. fM) for detection of BRCA1 5382 mutation by EIS method. Under the optimum conditions, the suggested biosensor revealed high selectivity for discriminating the complementary sequences from non-complementary sequences. (C) 2016 Elsevier B.V. All rights reserved.