The thermoelectric effect, otherwise known as “Seebeck effect”, is the direct conversion of a temperature difference between two dissimilar electrical conductors or semiconductors to an electrical voltage. By making use of this process, the thermoelectric generator (TEG) becomes a promising technology for the waste heat recovery. Compared to other energy-harvesting technologies, TEG exhibits distinct advantages such as it can be used remotely, can operate in silence and no gaseous or chemical waste is produced during operation. An ordinary TEG contains multiple couples of one p-type and one n-type thermoelectric unit. Therefore in order to build a TEG, choosing thermoelectric (TE) materials either inorganic or organic becomes the top priority. As the most common inorganic TE material, PEDOT:PSS has received an extensive scientific interest in recent years. This review covers the motivation of developing organic thermoelectric generators (OTEG), techniques for PEDOT:PSS material preparation, material properties' measurement and analysis, and the thermoelectric performance optimization process. Finally, some challenges and future expectations are provided for further levels of development.