Polymeric films with different conductivities are widely used as coatings on electronic devices. For the reliability of their application, evaluation of mechanical properties is essential. In this paper, mechanical properties of conducting polythiophene (Pth) films are investigated with Scanning Electron Microscopy (SEM) to understand the relation between the mechanical properties and the electrochemical polymerization (ECP) deposition process and microstructure as well as film thickness. An attempt to explain the special properties exhibited by films with different thickness is made. The fatigue microcrack initiation and growth around a cross indent was observed in low cycle tension-tension fatigue tests. Three typical fatigue fracture models (short micro crack propagation, spallation and fragmentation) for films deforming coherently with the stainless steel substrate have been directly observed with SEM and conditions for their occurrences are discussed.