Abstract: Carbon black (CB) and carbon nanotubes (CNTs) were used as additives in phenolic resin. The effects of the additives and heat treatment temperature on the oxidation resistance and structure of carbon from the pyrolysed phenolic resin were investigated by differential scanning calorimetric analysis, X-ray diffraction, scanning electron microscopy, and mercury intrusion porosimetry. It was observed that both CNTs and CB improved the graphitization degree and oxidation resistance of the pyrolytic carbons. The graphitization degree of carbons containing CNTs was higher than that of those with CB, but the oxidation resistance of the former was lower due to the higher porosity in the microstructure. An increase in the heat treatment temperature also resulted in an improvement in the graphitization degree and oxidation resistance of the carbons.