Polyacrylonitrile/zirconium dioxide (PAN/ZrO2) nanocomposites were synthesized by dispersion of ZrO2 nanoparticles through the in situ emulsifier-free emulsion polymerization technique. The thermal stability of PAN/ZrO2 nanocomposites was enhanced with increasing concentrations of ZrO2 which may be due to dispersion of nanoparticles in PAN matrix. The electrical conductivity of nanocomposites gradually increased with increase in the ZrO2 loading. The gas barrier property of PAN/ZrO2 nanocomposites was determined by using gas permeameter and it was found that, the gas barrier property was reduced to about 10 times with increase of ZrO2 proportions. This is because ZrO2 nanoparticles in PAN/ZrO2 nanocomposites created a tortuous path for preventing oxygen permeation. The electrical conductive PAN/ZrO2 nanocomposites may be used in semiconductor devices and packaging materials.