In this work, the effect of the cross-section of carbon fibers on the thermal characteristics of carbon fiber-reinforced composites has been investigated. The thermal characteristics of the composites are much affected by cross-sectional shape and heat treatment temperature of the reinforcements. In case of round shape carbon fiber-reinforced composites (R-CF/EP), the thermal anisotropic factor shows nearly 53, while that of hollow shape (H-CF/EP) and C shape (C-CF/EP) shows about 118 and 130, respectively. Therefore, both H-CF/EP and C-CF/EP have an excellent directional thermal conductivity to distribute heat above 200%. This result from the higher shear stress during spinning of anisotropic pitch-based hollow and C shape carbon fibers, which induce higher molecular orientation along the fiber axis than that in round shape fibers. And, with increasing heat treatment temperature, the thermal diffusivity of non-round types composites is much superior to that of round shape composites. This is probbly due to the rearrangement of molecular structure resulting in graphite-like structure and higher thermal conductivity along with the fiber axis direction. Also, the thermal anisotropic factor of the above systems follows the mixing law.