Thermal modulation voltammetry (TMV) using laser heating at a liquid/liquid microinterface is a useful technique for determining the standard entropy change of ion transfer. In this work, for achieving TMV using a visible laser as a heating source at a 1,2-dichloroethane (DCE)/water microinterface, we used an optically absorbing supporting electrolyte, i.e., crystalviolet tetrakis(4-chlorophenyl)borate (CVTClPB). CVTClPB served well not only as a supporting electrolyte but also as an optical absorber in the DCE solution, and thereby, well-defined linear sweep (LS) and TM voltammograms could be obtained. On the basis of LS and thermal modulation (TM) voltammograms obtained with CVTClPB, the standard entropy changes of ion transfer for six model ions were successfully determined.