In this study, polyselenophene (PSe), which has more raw materials, lower cost, and can be processed more easily than inorganic thermoelectric materials, was synthesized as a polymeric thermoelectric material with a simple method by chemical oxidative polymerization in aqueous medium. Copper sulfide (CuxS) was synthesized and taken from it in different ratios compared to PSe, PSe/CuxS composites were prepared. The Seebeck coefficient of PSe is 160 μVK-1, while that of PSe/CuxS composite containing 30% CuxS is 410 μVK-1. The PSe/CuxS3 composite with 30% CuxS had the highest Seebeck coefficient and power factor, measuring 410 μVK-1 and 5043 μWm-1K-2, respectively. The electrical conductivity of PSe and PSe/CuxS composites obtained in this study is relatively high, ranging from 10 - 405 Scm-1. PSe and its composites were characterized by FTIR, UV-Vis., XRD, TGA, EDX, and FESEM.