This work presents a new patterning technique of Indium Tin Oxide (ITO) thin films using the microelectrode of a Scanning Electrochemical Microscope (SECM). With the development of new display technologies, patterned indium tin oxide (ITO) films have enormous growth potential and can find applications in any device that requires transparent and conductive electrodes. To optimize the performances of such devices, a clean patterning technique providing straight sidewalls and control of surface chemistry and physical properties is needed. We report here a simple and one-step patterning technique of ITO using scanning electrochemical microscopy as a soft etching tool. This electrochemical wet-lithographic technique provides a fast and low cost patterning process and is performed in an aqueous acid electrolytic solution. This maskless technique leads to a clean etching with straight walls and no redeposition of the ablated part. The subjacent substrate (glass or polymer) is not damaged by this technique and the electrical and/or optical properties of the remaining ITO film are preserved