Thermoelectric (TE) composites are emerging materials with unique capability to directly convert heat to electricity. Poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT) has received increasing attention for TE application. Relative to inorganic counterparts, organic polymers and their composites have various advantages of low heat conductivity, element richness and high adjustability in both molecular structure and processing method. In particular, PBTTT can be processed by both solution and melting techniques. In this review, we focus on the recent progress of PBTTT TE composites. The synthesis technique and PBTTT's basic properties are firstly introduced. Then, the TE performance of the neat PBTTT are discussed. After that, we mainly summarised the recent advances in PBTTT TE composites with carbon nanotubes or graphene as the inorganic constituents. Finally, the research challenges and future prospects are outlooked.