Natural rubber, as well as natural reinforced rubber, with different carbon nanotubes concentrations, 10 and 20 mm, thick, have been structurally, chemically, and thermally investigated. Scanning electron microscopy techniques, as well as X-ray energy dispersive analysis, Raman, and thermal conductivity analysis, were used in characterizing materials in order to establish a connection among the CNT concentration, homogeneity of reinforcing elements within the natural rubber, and their thermal conductivity characteristics. The theoretical approach reveals the dependence between the thermal conductivity and reinforcing elements. The final result confirms the increase of the effective thermal conductivity with the concentration of CNT.