A simple and cost-effective strategy to prepare Pd nanoparticle decorated glassy carbon electrodes is reported. Mechanically shortened fish sperm DNA molecules were used as effective nucleation templates for the deposition of highly dispersed Pd nanoparticles on glassy carbon electrodes. Atomic force microscopy (AFM) was employed to check the morphologies of as-deposited Pd nanoparticles. Electrocatalytic investigations revealed that the modified electrode using a DNA-based electroless deposition had remarkable catalytic activities toward the reductions of dissolved oxygen and hydrogen peroxide, as well as the oxidation of hydrazine. The DNA-assisted electroless deposition of Pd nanoparticles is expected to offer an easy, quick and low-cost strategy toward applications in fuel cells as well as electrochemical sensors.