Conducting polymers (CPs) have been extensively studied and widely applied in various organic devices. To improve the performances or extend the functions of the devices, CPs usually have to be nanostructured. Electrosynthesis provides an effective and convenient one-step approach to CP nanomaterials. The resulting materials are usually oriented on the electrode surfaces and their properties are easy to be controlled. This critical review focuses on the syntheses of CP nanostructures and nanocomposites by electrochemical polymerization. The applications of the nanomaterials in organic devices such as sensors, actuators and memory devices also will be discussed (111 references).