A new cationic poly(3,4-ethylenedioxythiophene)-DNA composite (P(EDOT-N)-DNA) has been prepared by in situ chemical oxidative polymerization of EDOT-N monomer in the presence of salmon DNA as template. Scanning electron microscopy shows that the P(EDOT-N)-DNA composite forms a porous pattern with a high surface area that is favorable for ion diffusion throughout the materials, which leads to improved capacitive activity. The P(EDOT-N)-DNA composite exhibits superior capacitance behavior as well as good charge-discharge reversibility. The P(EDOT-N)-DNA composite shows low cytotoxicity to living cells even at a concentration of 300 mg . L-1. The good biocompatibility of P(EDOT-N)-DNA imparts good potential as an environmentally friendly electrode material for energy storage devices, even in a biological environment owing to the combination of DNA with conjugated polymers.