The demand for electronic devices that are flexible and wearable is growing. To facilitate this demand, the next generation devices must be able to bend and stretch under mechanical loading. In this regard, energy harvesting technologies have invested in organic and polymeric semiconducting materials due to their, low cost and toxicity, good flexibility, tunable electronic properties and capacity for scaled manufacturing. For example, electrically conductive π-conjugated polymers have been investigated in various thermoelectric technologies for producing stretchable, wearable, and light-weight thermoelectric devices that can harvest energy from a temperature gradient and produce electricity with no pollution or moving parts. This review provides a general summary of the thermoelectric principles and conductive polymer characteristics, followed by the recent progress in their application in flexible and wearable thermoelectric devices. We also evaluate new advances in manufacturing hybrids of π-conjugated polymers with other polymers, inorganic materials, or carbon nanostructures, and their applications in body energy harvesting and smart cooling.