The amplified electrochemical sensing of DNA was accomplished by electrodeposited PEDOT on the electrode surface and incorporation of Nile blue (NB) as redox active intercalator into DNA. Herein, above modified electrode called as PEDOT/DNA/NB composite electrode. PEDOT/DNA/NB composite electrode exhibited well defined redox peak at − 0.35 V (Ag/AgCl) corresponding to NB. The composite electrode surface coverage (Γ) and ΔEp were compared with PEDOT/NB and DNA/NB modified electrode. Atomic Force microscopy (AFM), and cyclic voltammetry (CV) were used to characterize the PEDOT/DNA/NB composite electrode. The composite electrode was exhibited as surface confined redox process in neutral pH. The composite electrode was found to be pH dependent. The composite electrode exhibited catalytic property towards reduction of hydrogen peroxide (H₂O₂). The composite electrode was utilized to amperometric study and its response towards H₂O₂ detection was less than 6 s and the detection limit was 0.1 μM. Moreover, we tested PEDOT/DNA/NB composite electrode to electrocatalytic reduction of cytochrome c (Cyt c).