Conducting nanocomposites of poly (methyl methacryiate) (PMMA) and antimony doped tin oxide (ATO)were prepared by solution blending. The influences of ATO content on the electrical conductivity, thermal stability, and mechanical properties of the nanocomposites were investigated. A homogeneous dispersion of silane coupling agent modified ATO was achieved in PMMA matrix as evidenced by scanning electron microscopy. The resultant PMMA/silane-ATO nanocomposites were electrically conductive with significant conductivity enhancement at 4 wt pct. It was found that the composition at 4 wt pct ATO gave the higher tensile strength. Furthermore, it gave the largest elongation at break value among all the compositions.Thermal stability of the nanocornposites was remarkably enhanced by the incorporation of silane-ATO.