Abstract: With the unique ability to directly convert thermal energy to electricity or vice versa, the thermoelectric materials have exhibited great potential applications in waste heat recovery and environmentally friendly refrigeration. In contrast to the inorganic bulk thermoelectric materials, the flexible thermoelectric materials have the advantages of being bendable, small-size, light-weight and others, which makes them applicable in fabricating portable/wearable electronic device. In the recent decade, as one of the most challenging and promising functional materials, the conductive polymers, carbon materials and inorganic nanomaterials-based flexible thermoelectric materials and devices have attracted the attention of a great number of research groups around the world. This review describes systematically the recent achievements on flexible thermoelectric materials and devices based on different materials, and the problems that need to be solved urgently in the near future. The future major ongoing areas of effort have also been suggested. A large number of literatures have demonstrated that the thermoelectric performance of materials can be well-controlled through chemical synthesis and molecular design strategies, as well as morphology controlling and doping techniques. So far, research and development of the state-of-the-art flexible thermoelectric materials for practical applications still presents a considerable challenge.