With unique electrical properties and light weight characteristics, carbon nanotubes (CNTs) have attracted significant interest for thermoelectric (TE) applications. However, the self-aggregate and high thermal conductivity hinder the improvement of TE performance. Herein, we overview recent advances in the development of CNTs based organic TE composites, focusing on optimization strategies and the underlying mechanisms for the improvement of TE properties. The improvement of CNTs based organic TE composites are comprehensively overviewed from the perspective of dispersibility, doping engineering, and polymer incorporation. Additionally, the fabrication of the composites, composition regulating, morphology manipulation, fundamental studies for properties optimization, their TE properties, and device applications are emphasized. Finally, we present the challenges and prospects for the improvement of CNTs based organic TE composites, which paves a way for the applications of CNTs composites in sustainable energy harvesting systems.