We first report a simple and rapid electrochemical approach to synthesize novel nanofiber junctions and dendrites of conducting poly(o-phenylenediamine) without any surfactant or template. Through controlling some parameters such as the time and potential of electrodeposition and concentration of the reactant, nanofiber junctions and dendrites of conducting polymer can be easily obtained on the solid surface. This research provides a new method to synthesize complicated nanofiber junctions and dendrites on the conducting surface, which may find potential applications in nanodevice and electrochemical sensors.