A material capable of generating electric current through a temperature difference between its two ends is known as a thermoelectric material. Such materials must possess low thermal conductivity and high electrical conductivity simultaneously. In this study, coconut fiber, characterized by its low thermal conductivity, was combined with carbon nanoparticles, known for their high electrical conductivity, to fabricate a coconut fiber–carbon nanoparticle composite (denoted as Coconutfiber-nanocarbon Composite, abbreviated as CC). By adjusting the amount of embedded carbon nanoparticles, we aimed to develop a thermoelectric material with practical applicability. In one representative specimen, 150 aligned coconut fibers were compressed into a cylindrical composite with an outer diameter of 8 mm and a length of 10 mm, into which 80 mg of carbon nanoparticles were uniformly embedded (designated as CC80). This sample achieved a figure of merit (zT) as high as 0.23, approaching the threshold for practical thermoelectric applications. The thermoelectric current induced by a temperature gradient across the material reached its maximum value at a temperature difference of 21 K—a rarely observed physical behavior that can be attributed to the thermal motion of carbon nanoparticles. This study demonstrates that the coconut fiber–carbon nanoparticle composite is a promising, low-cost emerging thermoelectric material with significant potential for practical use.