Pd nanostructures have been synthesized by electrochemical deposition in a highly diluted solution. The morphology of the as-synthesized Pd nanostructures can be solely controlled by depositing potentials because the driving force for variable crystal nucleation and growth is only correlated with overpotentials. The as-prepared Pd nanostructures deposited at -0.25 V show a 3D feather-like dendritic morphology with a nanoscale structure, which exhibits high electrocatalysis activity towards ethanol electro-oxidation in alkaline media. Moreover, the present electrochemical method can be easily applied to fabricate other noble metal nanostructures.