Polythiophene-tinoxide (PT-SnO2) nanocomposites were prepared by in situ chemical oxidative polymerization, in the presence of various concentrations of SnO2 nanoparticles. Samples were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and Zeta potential measurements. Morphologies and elemental compositions were investigated by transmission electron microscopy, field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. The photoconductivity of the nanocomposites was studied by field-dependent dark and photo conductivity measurements. Their dielectric properties were investigated using dielectric spectroscopy, in the frequency range of 1kHz-1 MHz. The results indicated that the SnO2 nanoparticles in the PT-SnO2 nanocomposite were responsible for its enhanced dielectric performance. © 2016 Elsevier Ltd.